Storage and UseFor San Luis Obispo and Santa Barbara County

Port San Luis Light House built in 1890 utilizes an impervious surface to collect rainwater which gravity feeds underground concrete storage tanks seen here.

A series of wood wine barrels capture water for landscape irrigation in the dry season at Camp Ocean Pines in Cambria. Overflow from the barrels and the downspouts are directed to a rain-garden.

This Los Osos residence captures rainwater from the roof with a downspout diverter. Harvested rainwater is used for landscape irrigation.

Harvesting the Rain

San Luis Obispo ~ Coalition of Appropriate Technology’s Guide to

Suggested donation: $10.00

The California Conservation Corps installed a large rainwater harvesting system on their campus behind Cuesta College. This metal collection tank is capable of holding 30,000 gallons, which feeds their nursery.

Funding for this project has been provided in part by the Morro Bay National Estuary Program with funding from the U. S. Environmental Protection Agency, SLO-COAT members, individual companies shown above and the City of Santa Barbara.

This is the third publication in an educational series regarding water and waste applications of appropriate technology for San Luis Obispo County and now Santa Barbara County as well.

These guidelines are being developed by the San Luis Obispo Coalition of Appropriate Technology (SLO-COAT) to specifically address efforts to maintain a healthy hydrological cycle throughout the Central Coast.

SLO-COAT is a joint effort of SLO Green Build, the San Luis Bay Chapter of the Surfrider Foundation, SLO Permaculture Guild and the Santa Lucia Chapter of the Sierra Club. The information presented is for general education purposes. Final details and construction must be developed and designed for specific site conditions; therefore SLO-COAT is hereby indemnified from any liability arising from the use of this information.

Cover image- photo credits: Port San Luis Lighthouse cistern- San Luis Sustainability Group, Los Osos residential rain barrels- Lawson Schaller, California Conservation Corps Cistern at Cuesta College - Alex Vincent, Rain barrels and rain garden at Ocean Pines Camp cabins in Cambria - San Luis Sustainability Group.

San Luis Sustainability Group

appropriate technologysustainable planninggreen architecture

San Luis Obispo Coalition of Appropriate Technology’s Guide to

Harvesting the Rain: Storage and Use© June 2013

Appropriate technology is defined as applying technology to address problems related to energy use, the water cycle, and affordable building at the smallest and most accessible scale possible.

The water imbalances in San Luis Obispo and Santa Barbara Counties have become evident as many municipalities implement water rationing policies. Growth has always been naturally restrained due to the scarcity of water resources in our counties. New development is often burdened with the subsequent increase in infrastructure costs. Fortunately, over the past thirty years, the research and refinement of appropriate technologies as related to water have much to offer us today.

SLO-COAT believes it is imperative that we revisit, at a local scale, the encouragement and application of appropriate technology. Both counties are in a position to be at the forefront of these efforts to reconcile growth and environmental quality.

Application of appropriate technologies as described in this guide can improve our connection to water and maintenance of a healthy hydrologic cycle. Key terms appear in bold italic and are defined in the glossary at the end of this guide. In addition to Harvesting the Rain, appropriate technology topics related to healthy watersheds and water cycles are:

GraywaterRainwater Management for Low Impact Development (LID)

Waterless Waste Treatment

Look for more information and educational events presented by SLO-COAT on these topics. If you would like to become involved, find SLO Green Build online at www.slogreenbuild.org

Contributing authors of SLO-COAT: Ken Haggard- Architect & Planner San Luis Sustainability Group, Mikel Robertson- General Contractor & Green Building Material Specialist Green Goods, Rachel Aljilani- LEED AP, Alex Vincent- Permaculture Designer.

Special Thanks to:Brad Landcaster, Art Ludwig, Brock Dolman, Nate Downey, Mark Lakeman and Johnathan Todd who have helped educate our community on the current trends in appropriate technology applications and regulations. This would not be possible without the ongoing support of SLO-COAT members and peer reviewers: Mladen Bandov, Andrew Christie, Lawson Schaller, Joshua Carmichael, Pat Renshaw, Teresa Lees and the numerous community members also concerned about water resources and sustainable development.

NATURAL HYDROLOGIC CYCLE

No matter where you live, you live in a watershed, and are part of a hydrologic cycle. A natural hydrologic cycle and healthy watershed work hand in hand to create a clean, healthy environment that supports complex social, economic and ecological systems.

A watershed is a basin that funnels water from ridge tops to the ocean. The hydrologic cycle occurs in a watershed and provides fresh water in the form of precipitation (rain, hail, snow) and condensation (fog). Water collects in riparian areas forming creeks and streams, and infiltrates into the ground replenishing aquifers. An aquifer is an underground layer of rock or soil in which groundwater resides. Aquifers can provide substantial amounts of potable water but many are overdrawn.

WATER RESOURCES- AVAILABILITY CONCERNS

Water availability in our two counties is a serious problem. Without creative responses on all of our parts, it is destined to become worse due to climate change, seasonal irregularities and population growth. Already several of our communities are impacted by these problems like Cambria, Nipomo and Los Osos. With continued drought cycles, this number will increase substantially.

Rainwater harvesting is a way to stretch a county’s natural water budget and can be a big part of being more creative with our limited water resources. Most people don’t realize how much effect rainwater harvesting can have even in the dryer parts of our county until they do the simple calculations illustrated on page 2 of this guide. By collecting and storing rainwater we can reduce rapid pollutant filled run-off into our oceans and creeks and reduce our water demand from remote sources during dry periods.

PACIFIC OCEAN

COASTAL WATERSHED

CAMBRIA CAYUCOS SAN LUIS OBISPOMORROBAYLOS

OSOS

Green Valley, Los Osos Valley, Chorro Valley, Edna Valley, Arroyo Grande, Huasna Valley, Nipomo Valley, Cuyama &

Santa Maria Rivers

CUESTA RIDGE

WEST TO EAST SECTION

HIGHESTRAINFALL

precipitaion

aquifer recharge

aquifer rechargesalt water intrusion

fog condensation

evaporation

I

BENEFITS OF HARVESTING THE RAIN

1. Reduce the water bill for your home or business

2. Capture water for passive & active landscape irrigation

3. Add aesthetic interest to your yard

4. Protect your community’s wildlife, soils, creeks, lakes & watersheds

5. Help your community by reducing off-site flooding problems and reducing the

extent of municipal stormwater infrastructure; thereby saving public funds

6. Reduce pollution entering the surface waters

7. Recharge groundwater aquifers

SALINAS RIVER

RAINFALL

INLAND WATERSHED CLOSED WATERSHED

GRADIENT

ATASCADEROPASO

ROBLES

SODA LAKE

CARRIZO PLAINSALINAS VALLEY

CARRIZO PLAIN

THROUGH SAN LUIS OBISPO COUNTY

LOWESTRAINFALL

precipitaion

aquifer recharge

SANANDREAS

FAULT

SAN MIGUEL

non-potablewater

Santa Barbara (SB) County has a similar profile section as the one shown above for San Luis Obispo (SLO) County. Wet areas along the coast are separated by mountains form a progression of drier valleys as one proceeds inland. For example, the Santa Ynez Valley is similar to the leeward side of the Cuesta Grade and the Cuyama Valley greatly resembles the Carrizo Plain.

II

The long history of rainwater collection, can be traced (in recorded history) as far back as ancient times some 3,000 years ago (850 BC) if not even farther. Yet today, as long as water is not a problem, people don’t really seem to care where it comes from or even how it gets into the house, just as long as it is there and useful.

When we develop communities, we create impervious areas which inhibit the absorption of rainwater into the ground and local aquifer. It also diverts water that once made its way to a creek or stream. Although the increase in impervious surfaces creates difficulties such as increased water run-off during storms, this doesn’t need to be the case. Rainwater harvesting is perfect for pairing with impervious surfaces if those surfaces are adequate for becoming rainwater collection components.

If the history of rainwater collection tells us anything of value, it is that filtration is the most important component in any harvesting system. Different collection surfaces and environments allow you to catch water of various qualities. Understanding which contaminants might be in the water you harvest and how to filter it for the intended use are necessary for health and safety.

Rainwater harvesting regulations will vary in urban and rural settings. Be sure to double check with your local building and health departments to make sure you can use your rainwater for the intended use. Rainwater is used in both potable and non-potable uses within the county, but potable uses require extensive filtering, treatment and engineering whereas non-potable uses such as landscape irrigation systems often require less filtering and treatment.

Contact information is located on the back cover of this publication to assist you in connecting with your local jurisdiction to make sure you have a safe and healthy rainwater harvesting experience.

WHAT IS RAINWATER HARVESTING?

Rainwater:Problem or Resource?

The first heavy rainfall brings a first f l u s h o f n o n - p o i n t s o u r c e pollution as illustrated by the outfall pictured below along the Embarcadero in Mor ro Bay. Samples and testing analysis conducted by the Morro Bay National Estuary Program showed E. coli levels varied in 2009 from 1,223 to 7,701 MPN/100 mL. The standard for safe swimming is 235 MPN/100 mL. Capturing rainwater and using it on site helps reduce the amount of rainwater that enters storm-water management systems, like curbs and gutters that drain to the ocean.

Harvesting rainwater can effectively reduce the density of pollutants at first flush locations by reducing the quantity of stormwater that carries bacteria, heavy metals from cars, pesticides, pet waste and other non-point source pollutants that make their way via stormwater into sensitive aquatic habitats, such as estuaries, streams and the oceans. In addition, rainwater harvesting restores some of the filtration that occurs in natural environments that is lost by development.

III

STEP 1: Baseline Conservation 1

STEP 2: Calculating Rainwater Harvesting Potential 2-4

STEP 3: General Design Considerations 5

Regulations and Small Scale Rainwater Harvesting Systems 6

Large Scale Rainwater Harvesting Systems 7-8

I. Collection Components

1. Collection Surfaces 9-10

2. Gutters 11-12

3. Downspout Diverters 12

II. Cleaning Components

4. First Flush Devices 13

5. Filters 14

III. Storage Components

6. Storage Tanks 15-17

7. Mosquito Screens 17

IV. Use Components

8. Water level indicators 18

9. Pumps, Access Pipe & Auto-fill 18

10. Treatment (UV Filters) 18

Glossary 19

Product Resources 20

TABLE OF CONTENTS

Kitchen

Scrape rather than rinse dishes before placing them in the dishwasher.

Do not thaw frozen food under running water.

When hand washing dishes, fill one basin with soapy water and the other with rinse water. Avoid running water continuously while washing dishes.

Install Energy Star rated dishwasher and only wash full loads.

Laundry

Install Energy Star clothes washer and set water volume to the minimum requirement per load. Use a clothes rack or line to dry your clothes if possible.

Use short water cycles for lightly soiled loads.

Pre-treat stains to avoid multiple washings.

Soak heavily soiled items in a sink one third full to prewash.

Bathrooms

Check for leaks from pipes and faucets, the smallest drip can waste up to 2 gallons per day!

Install dual-flush or ultra low flow toilets.

Install low-flow faucets, shower heads and faucet aerators.

Turn off water while brushing your teeth and shaving.

Take 5 minute or shorter showers and turn water off during and while soaping.

Waterless urinals, composting toilets or dry vaults are very appropriate and becoming legal and applicable.

Outdoors

Use graywater in your landscape like a laundry to landscape system.

Plant drought tolerant or xeriscape landscapes.

Before incorporating rainwater into your lifestyle, first start off by adopting a baseline conservation plan. Conservation is the most affordable technology and practices are readily available that require little if any behavior change. Most water providers have programs to help you conserve by offering free or discounted low flow shower heads, faucet aerators, toilet tummies and more.

While this document does not attempt to provide a thorough cost benefit analysis, we recognize it is a worthwhile consideration. Costs and benefits will vary greatly depending on the rainwater system selected, the local cost of water and volume utilized. Simple systems are low cost and can be done by the homeowner with few new parts and supplies, or by integrating salvaged or used materials. Other systems are more complex, requiring professional installation, and expensive components. Regardless of the system selected and the volume utilized, the user will have the satisfaction and benefit of reusing water, helping the environment, and having a drought resistant supply during mandatory watering restrictions.

Water auditing is an important technique for determining water usage. It is helpful for identifying areas where water is being wasted. Sometimes one small faulty component in a toilet or irrigation system could be costing you several gallons of water each day. Studies estimate leaks account for 18% of residential water consumption. Ample resources and training are available to help you with both indoor and outdoor water audits. After accounting for water uses and losses, strategies can be identified for conserving water which means lower water bills.

STEP 1: BASELINE CONSERVATION

1

First, using the rainfall map for San Luis Obispo or Santa Barbara County on page 3 or a number of on-line weather data resources, you can determine your average rainfall per year. For example, Los Osos shows an average rainfall contour of 18 inches per year on this map. Convert inches to feet by diving by 12. Los Osos then has an average of 1.5 feet per year of rain.

Then examine your collection surface to determine the area of collection. For example, if you have a roof surface that is 20 feet by 50 feet than your collection area would be 1,000 square feet.

Now multiply your average rainfall per year by the collection area. For Los Osos this is 1.5 feet multiplied by 1,000 square feet, so you can collect 1500 cubic feet of water.

To make this number more meaningful in terms of gallons, you will need to convert cubic feet to gallons. There are 7.48 gallons per cubic foot. So for the Los Osos example, we’ll multiply 1500 cubic feet by 7.48 gallons per cubic foot and discover that this relatively small collection area can capture 11,220 gallons per year.

The other consideration is the water lost by the first flush device, this is usually 10 gallons for every 1,000 square feet of collection surface (see page 13). So for our Los Osos example, we can probably capture 11,205 gallons.

In some areas of SLO County like Adelaide where the average rainfall is 42 inches per year, rainfall is 2-3 times as much as Los Osos while in other areas like the California Valley it is less than half as much, only 8 inches per year.

With a small area of 1,000 square feet, it is possible to capture anywhere from 5,000- 26,000 gallons of water per year. Most sites will have much larger collection areas and much greater potential for harvesting the rain.

Rainwater harvesting can be appreciable, if a large enough cistern is used in conjunction with baseline conservation measures, many of the buildings in the Central Coast could be self-sufficient and operate strictly off rainwater.

How Much Rain Can I Expect to Capture?

#3- Calculate cubic feet of water1,000 ft2 x 1.5’ = 1,500 ft3

#4- Convert cubic feet to gallons1,500 ft3 x 7.48 gal/ft3 = 11,220 gal

#5- Subtract first flush loss11,220 gal - 15 gal = 11,205 gal

#2- Calculate collection area20’ x 50’ = 1,000 ft2

#1- Convert rainfall to feet per year18”/ 12 = 1.5’

QUICK ESTIMATE:For simple estimating: for every 1” of

rainfall per 1,000 square feet of collection area, you can capture 620

gallons of water.

STEP 2: CALCULATING RAINWATER HARVESTING POTENTIAL

Los Osos Example:

This gives you a quick way to estimate rainwater capture. To see how far this amount will go in regard to landscape irrigation, see the calculations on the following page. We think you will be surprised how much can be done.

2

STEP 2: CALCULATING RAINWATER HARVESTING POTENTIAL

3

Annual Rainfall for San Luis Obispo and Santa Barbara Counties

Average rainwater available each year for regions within SLO and SB Counties(total gallons)

Average rainwater available each year for regions within SLO and SB Counties(total gallons)

Average rainwater available each year for regions within SLO and SB Counties(total gallons)

Average rainwater available each year for regions within SLO and SB Counties(total gallons)

Average rainwater available each year for regions within SLO and SB Counties(total gallons)

Average rainwater available each year for regions within SLO and SB Counties(total gallons)

Average rainwater available each year for regions within SLO and SB Counties(total gallons)

Average rainwater available each year for regions within SLO and SB Counties(total gallons)

North County[14 Inches]

North Coast[18 Inches]

South Coast[18 Inches]

San Luis Obispo

[24 Inches]

North County[13 Inches]

Santa Ynez Valley

[18 Inches]

Cuyama Valley

[8 Inches]

Santa Barbara

[18 Inches]

A 7,000 9,000 9,000 12,000 6,000 9,000 4,000 9,000

B 10,000 13,000 13,000 18,000 9,000 13,000 6,000 13,000

C 14,000 18,000 18,000 24,000 13,000 18,000 8,000 18,000

Roof Area Available for Rainwater Harvesting

A 1,000 Square Feet

B 1,500 Square Feet

C 2,000 Square Feet

Average rainwater available each year is based on published rainfall intensity data and 80% roof surface capture efficiency.Source: San Luis Obispo County Department of Public Works dwg #H-4 August 2006 & Hydrology Section, County of Santa Barbara

Rainwater can be used for landscape irrigation and, if properly treated, for indoor non-potable uses such as toilet flushing. Deciding on how you will use your harvested rainwater will determine the storage capacity you need and the correct selection of pumps, filters, and any other materials.

For landscape irrigation in your yard, determine how much rainwater you need by evaluating the landscaped areas where you will use the harvested rainwater, and then how much rainwater is available for harvesting.

Shown on the right is a map of rainfall inches per year for an average year. As can be seen, the amount of rainfall aries considerably over relatively small distances d u e t o t o p o g r a p h i c a l changes. You can use this information to calculate your specific rainwater harvesting potential as explained on page 2.

4

STEP 2: CALCULATING RAINWATER HARVESTING POTENTIAL

Relative Water Demand for Landscape Irrigation for San Luis Obispo and Santa Barbara Counties

Typical dry season (May-Oct) total water demand for regions within SLO and SB Counties(gallons per square foot of landscape area)

Typical dry season (May-Oct) total water demand for regions within SLO and SB Counties(gallons per square foot of landscape area)

Typical dry season (May-Oct) total water demand for regions within SLO and SB Counties(gallons per square foot of landscape area)

Typical dry season (May-Oct) total water demand for regions within SLO and SB Counties(gallons per square foot of landscape area)

Typical dry season (May-Oct) total water demand for regions within SLO and SB Counties(gallons per square foot of landscape area)

Typical dry season (May-Oct) total water demand for regions within SLO and SB Counties(gallons per square foot of landscape area)

Typical dry season (May-Oct) total water demand for regions within SLO and SB Counties(gallons per square foot of landscape area)

Typical dry season (May-Oct) total water demand for regions within SLO and SB Counties(gallons per square foot of landscape area)

North County[Paso Robles]

North Coast[Morro Bay]

South Coast[Arroyo Grande]

San Luis Obispo

North County[Guadalupe]

Santa Ynez Valley

[Santa Ynez]

Cuyama Valley

[Cuyama]

Santa Barbara

A 6 5 4 5 5 6 7 4

B 15 11 10 12 11 14 18 11

C 24 18 17 20 18 23 29 17

Total water demand is based on WUCOLS (Water Use Classification of Landscape Species published by the University of California Cooperative Extension, the Department of Water Resources and the Bureau of Reclamation, 2000.) methodology, using plant factors, irrigation efficiency, and reference evapotranspiration data.

Reference EvapoTranspiration

Zones

1 Coastal Plains Heavy Fog Belt

3 Coastal Valley & Plains

4 South Coast Inland Plains

6 Upland Central Coast

10 North Central Plateau & Central Coast Range

16 Westside San Joaquin Valley

Consult a landscape professional or use the following table as a guide to estimate the water demand for the landscape planting types and the climate specific to your location. On California’s Central Coast, the dry season is typically May through October, which has very little rainfall. Most of the harvested rainwater is

captured during the wet season and used during the dry season. For example, a high water landscaped area of 400 sq. ft. in Santa Barbara could require 6800 gallons during the dry season. A 1,000 sq. ft. roof could collect 9,000 gallons of water, more than enough for a thirsty landscape!

Landscape planting

A CA native/adapted (low water needs)

B Ornamental garden (moderate water needs)

C Turf or tropical (high water needs)

5

STEP 3: GENERAL DESIGN CONSIDERATIONS

Small Scale Rainwater Harvesting

1

23

4

5

6

7

89 10

There are some basic design considerations to take into account when combining rainwater system components. The most important factor is to keep the water that you collect clean and healthy. In natural environments there are large amounts of dust, pollen, animal feces, dead insects, animals and leaves, but there is also an overwhelming amount of natural filtering and cleaning that occurs. Most of this filtering occurs through thatch, leaves, gravels, soils, etc. This is why streams in their natural state are almost always clean. Our main goal in designing a rainwater harvesting system is to replicate what occurs in nature at the scale of the individual building. Therefore, all these components must work together to reduce contaminants and ensure filtration at many levels.

To design a rainwater harvesting system you must look beyond your roof or catchment surface and examine the micro-bioregion of your site. Walk outside and note the location, size and species of nearby trees. Learn about the fruit, flowers and leaves that may seasonally drop onto your catchment area. Ask yourself, does the proximity of the road

I. Collection1. Roof Surfaces2. Gutters

II. Cleaning Components3. Downspout Diverters4. First Flush Devices5. Filters

III. Storage Components6. Storage Tank7. Mosquito Screen

IV. Use Components8. Water Level Indicators9. Pumps, Access Pipe & Auto-Fill *10.Treatment

* Not used in most basic systems

create dust and debris? Can you modify the situation by planting screening and filtering vegetation? Take note of birds, squirrels, raccoons, and other wildlife. What are the local insects? Note local wind patterns. Get a feeling of all the stuff collecting on your roof and with each step of the rainwater catchment system what you need to filter.

When using the roof of a house as a catchment surface, it is important to consider that many roofs consist of one or more roof “valleys.” A roof valley occurs where two roof planes meet. A roof valley concentrates rainfall runoff from two roof planes before the collected rain reaches a gutter.

Like any system, to keep it healthy requires maintenance. Annual cleaning before the rainy season reduces the possibility of clogging and overflows which can effect the purity of the water. Make sure to sweep valleys in the roof and take note of and repair peeling paint, loose shingles and miscellaneous debris. Clean at flashing locations, chimneys, vent pipes, satellite dishes, skylights and other protruding surfaces.

Overflow

6

REGULATIONS & SMALL SCALE RAINWATER HARVESTING SYSTEMS

Building codes and regulations are undergoing constant change, so it is important to check with your local jurisdiction before installing any rainwater harvesting system. California generally allows small scale residential systems under the plumbing code to be exempt from permitting if:

Water is intended for irrigation only

Tanks are supported on grade

Tanks do not exceed a height-to-width ratio of 2:1

Total capacity does not exceed 250 gallons

Tanks are labeled with signs for non-potable water

Non-potable water does not interact with potable water systems, building sanitary sewer systems or drainage systems that flow to a creek

Rain barrels and smaller capacity tanks can be linked together to achieve a greater capacity. It is important to remember to manage overflows properly with both small and large scale systems. A rain garden or swale can direct overflow from small systems into planted areas that provide aesthetic value and help recharge groundwater (see SLO-COAT Rainwater Management Guide).

Systems used for irrigation that rely on gravity are the simplest and will require the least amount of maintenance and energy. Once you add pumps and other electrical components to your rainwater harvesting system, you will likely need building permits. Even large amounts of grading can require permits, so please check with your local building department to help protect yourself and others.

Uses for harvested rainwater and the level of treatment before use should also be verified with local officials. Irrigation, car washing, laundry and toilet flushing needs can be met with non-potable water

that has been treated to a level suitable for those uses. Backflow prevention and cross connection are the primary concerns when rainwater is used in parallel with potable water systems, so additional measures must be taken to insure separation (see Use Components, pages 18-19 of this guide).

Numerous resources are out there to help explain how to build a rainwater harvesting system, but it isn’t a one size fits all system. Every situation will vary based on the location, collection surfaces, storage capacity, toxins, allowed uses, etc., so asking an expert how to go about designing your rainwater harvesting system is a great idea.

Maintenance is a reality with all rainwater systems regardless of scale, so be prepared to do this yourself or have someone help you with maintaining the various components of your system. A quick overview of maintenance items are presented below:

Collection surfaces are clear of debris

Gutters and screens are clear of debris

First flush devices emptied

Overflow routes are able to accept water

Storage components do not leak

Filter fabrics are not accumulating bacteria

Mosquito and rodent screens are in place

Pumps work properly

Carbon and UV filters are properly maintained

Non-potable water and rain harvesting signs are intact

Your storage containers are not full of odd colored water and foul odors *Remember, clean water is colorless and odorless

Enjoy using your system

7

LARGER SCALE RAINWATER HARVESTING SYSTEMS

springs

swaleswale

pump house

high storage

Rural LandsWater Sequence(1) In-Ground Catchment(2) Screen & Pre-Filter(3) Initial Storage(4) Filtration(5) Storage Tank & Pump

For large scale applications with significant acreage and large storm water capture potential, storage in carefully located reservoirs formed with ground contours are most cost effective. The main concern with these systems is the large losses due to evaporation, about 10% per week minimum.

In higher density housing, parks, greenways and roof surfaces can all become collection surfaces. This water may be more polluted and should be restr icted to landscape irrigation. Underground storage tanks can be placed under parking lots and driveways, but need to be rated to avoid damage from surface loads.

reservoir

(1) Pre-Filter (2) Tank (3) Pump (4) Sand Filter (5) Larger Tank (6) Pump

High-Density HousingWater Sequence

underground tanks

Large commercial situations provide ample collection surfaces with roofs, parking lots, plazas, etc. Large underground storage tanks, pumps and additional filtration and purification are typical in these systems.

Reservoir systems should utilize gravity flow whenever possible. Historic farms on the central coast illustrate this principle with the vertical arrangement of well, pump house, storage tank and windmill.

Commercial Lots

Three generalized large scale approaches to ra inwa te r harvesting are shown here. A rule of thumb for estimating the cost of a system is usually $1/gallon collected, but this will vary considerable with the scale and context of your situation.

No Mixing!

Remember that any system needs to a v o i d m i x i n g g r a y w a t e r a n d harvested rainwater.

8

LARGER SCALE RAINWATER HARVESTING SYSTEMSAll reservoirs should consider the following: 1) depth to surface area ratio- a greater depth and less surface area will reduce the losses from evaporation, 2) erosion and pollution- these should be minimized in the catchment area, 3) fencing- to keep livestock out and for other safety reasons, 4) gravity fed outlets- reduce maintenance and increase efficiency of the system. Three approaches to reservoirs are shown below.

Earthen dam : Use of a natural depression or gully to contain water held by soil that was graded to make the basin. Soil type needs to limit seepage and be capable of carrying the weight of the dam wall. A clay layer may need to be added if the soil is too porous. There should be no ant hills, p i ts , sewage out le ts , sa l ine or calcereous soil at the site. Provide two spillways to prevent damage from washouts in large storms.

Rock catchment dam: Massive unjointed rock outcrops can provide excellent catchments and holding surfaces. Soil and vegetation on the rocks should be removed from the rock surfaces and any large joints or cracks should be sealed with mortar or bentonite clay. Run-off can be channeled by rock or concrete gutters or groves cut into the rock.

Groundwater dam: This approach uses large deposits of sand near a natural water course to hold the water underground but near the surface. It can be enhanced by using a masonry wall or a subsurface clay dam to build up sand in a large pocket that can be filled with run-off water. One advantage is that surface evaporation is greatly reduced which is very beneficial during long dry periods.

silt traps

outlet pipe

spillway with rock apron

reservoir

f i l ter box

c lay wall

spillway

Use of harvested rainwater for potability requires three phases of treatment:

#1charcoal filtration to remove bacteria

#2UV light to kill microbes

#3fine screening to

remove small particles

new level

former level

sand pocket stone or ground gutters

reservoir utilizing an inselberg type stone outcrop

1

Underground Storage Tank1. Collection point2. In-Ground First-Flush Filter3. Non-Return Valve4. Smoothing Inlet5. View & Maintenance Ports6. Stainless-Steel Suction Filter Floor7. Tank hold-Downs8. Submersible Pump9. Overflow Valve10.Pressure Tank

2

34

5 5

6

7 7

8

9

10

To Overflow

From Plazas,Roads, Roofs,Parking, Etc.

Typical underground storage tank for commercial application utilize a plastic tank. These tanks are available in a variety of sizes and shapes. Alternate large scale cellar systems for holding water under permeable paving is shown on page 19 of SLO-COAT”S Rainwater Management for Low Impact Development Guide.

To Point

of Use

collected from reverse side

9

1. Roofs for Rainwater CollectionThe roof of a building is the first choice for collection. Water quality from different roofs is a function of the type of materials and local micro-climate conditions. Roof surfaces come in two general types, impervious to water and permeable surfaces of various degrees. Impervious roofs are the most desirable for rainwater collection because permeable roofs are more likely to collect dust and debris and are more difficult to clean. It is important to minimize any dirt, debris or chemicals that could contaminate the water so that filtration can be minimized later in the process. Below we list various types of roof surface in order of their suitability for rainwater collection:

A. Metal The quantity of rainwater that can be collected from a roof is in part a function of the roof texture, the smoother the better. A commonly used roofing material for rainwater harvesting is sold under the trade name Galvalume®, a 55 percent aluminum/45 percent zinc alloy- coated sheet steel. Galvalume® is also available with a baked enamel coating, or it can be painted with epoxy paint. Some caution should be exercised regarding roof components. Roofs with copper flashings can cause discoloration of porcelain fixtures and is not desirable for potable uses.

I. COLLECTION COMPONENTS

Standing Seam Ribbed Corrugated

B. SlateSlate’s smoothness makes it ideal for a catchment surface for potable use, assuming no toxic sealant is used; however, it is expensive so cost considerations may preclude its use.

C. ElastomericElastomeric surfaces are rubber like and commonly used for sealing flat roofs that are used for walking (decks, balconies, etc.).

D. Clay or Concrete TileClay and concrete tiles are both porous and easi ly avai lable materials that are suitable for potable or non-potable systems. They may, however, contribute to small water loss due to texture, inefficient flow, or evaporation. To reduce water loss and prevent bacterial growth on porous materials, tiles can be painted or coated with a sealant, which may also contain toxins that leech into the water.

E. Living or Green RoofsEarthen roods planted with a variety of plants, succulents, grasses and flowers help cool a roof and create social space. Subsurface cells allow additional drainage during heavy rain periods and divert water to gutter sources.

F. Composite or Asphalt ShingleDue to l each ing o f t ox i ns , compos i te sh ing les are not appropriate for potable systems, but can be used to collect water for irrigation. Composite roofs have an approximate 10-percent loss due to inefficient flow or evaporation.

1

2

Photo Credits:1 Mystic Grey Slate Roof in Canada, Westone Slate2 Elastomeric Roof, Michael R. Allen

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G. Tar or GravelA built up roof consisting of layers of tar and gravel are a commonly used surface on low slope roofs. Due to potential toxins in the tar and the debris-holding and flaking characteristics, this type of roof along with composite roofs is not recommended for potable systems. These roofs have an even higher loss rate due to inefficient flow and evaporation.

H. Wood Shingles or ShakesWood shingles are not very desirable for water collection due to their short life span. They also are capable of producing a lot of debris and can ha rbo r mo ld . F i re protection requirements also restrict their use in high fire severity zones. Treatments to protect the shingles from fire are often very toxic with high VOC levels and will add contaminants to the water running off of them.

Alternative MaterialsWith the ever increasing demand for “Green Building Products”, new materials are emerging containing recycled content and rapidly renewable materials that are non-toxic and have a lower embodied energy. One such example is rubber roof tiles made from old tires. Toxicity of such materials need to be checked before water is to be used for purposes other than irrigation.

Collection Surface Collection Efficiency

Potable Options

Expected Life

Flammable Cost Absorbs Pollutants

Metal Seam +++ Yes +++ No $$$ No

Corrugated Metal +++ Yes +++ No $$ No

Natural Slate ++ Yes +++ No $$$ Yes

Elastomeric Roof +++ Yes +++ Yes $$$ No

Clay or Concrete Tile + Yes ++ No $$ Yes

Living or Green Roof + No ++ No $$$ Yes

Asphalt Shingle + No + Yes $ Yes

Tar & Gravel + No + Yes $ Yes

Wood or Shingle Shake + No ++ Yes $$ Yes

Plastic Tile ++ Yes ++ Yes $$$ No

Other Collection SurfacesBeyond your building’s roof, one can collect rainwater from other structures, decks and paved areas. In urban areas, plazas, parks, and parking lots have been used for water collection. Debris in the form of trash and toxic drippings from cars make filtration and treatment much more important in these cases. Photovoltaic systems, either on roofs or stand-alone, also act as excellent collection surfaces.

+ = less, ++ = more, +++ = most, $ = least expensive, $$ = more expensive $$$ = most expensive

This table compares various collection surfaces and gives a relative rating for the attributes listed. Roof Surface Comparison Table

I. COLLECTION COMPONENTS

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Photo Credits:3 Shake Roof in Romania, Teveten

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2. GuttersGutters are installed to capture rainwater running off the eaves of a building. Gutters are important to protect the critical juncture between walls and roofs from water damage and are an integral part of any rainwater harvesting system. The most common materials for gutters and downspouts are galvanized steel, aluminum or PVC plastic. Many gutter installers provide seamless extruded aluminum gutters which have the advantage of not requiring waterproofing of joints in long runs.

Watch out! For potable water systems, lead cannot be used in gutter solders as is sometimes the case in older metal gutters. The slightly acidic quality of rain can dissolve lead and contaminate the water supply.

Other necessary components of a good gutter system are the drop outlet, which routes water from the gutters downward and 45 degree elbows which allow the downspout pipe to fit snug to the side of the building and brackets and straps to fasten the gutters and downspouts to the fascia and wall.

Gutters must be installed to slope toward the downspouts. The greater the slope the less likely of clogging so again it’s best not to have too long a gutter served by the downspout. Also the outside face of the gutter should be lower than the inside face to encourage drainage away from the building wall. Maintenance is very important because build up of debris in the gutter will reduce capacity and put additional gravity loads on the gutter which could result in sagging and overflow. Strategies to minimize overflow includes modification of the size and configuration of gutters and the addition of more drop outlets. Water diverters on part of the roof can sometimes be used to increase collection efficiency for the gutter.

Two of the most standard commercially available gutters are shown on the right. Custom larger size gutters are relatively easy to construct and can solve several problems. Maintenance is easier with a larger cross-section. They are easier to clean and have less blockage and clogging. Their greater capacity allows for more space between drop outlets and downspouts making connections to holding tanks easier. However, larger gutters require more structural support so the support system must be carefully designed.

I. COLLECTION COMPONENTS

Gutter Schematicroofroof edge flashinggutter supportgutterdrop outletdownspoutdownspout support

3-3/4”

3-1/4”Standard Ogee or K-style Guttercapacity 0.11 cu.ft./linear ft.0.82 gal./linear ft.

5-1/4”

5-8”

5-8”

Standard Half Round Guttercapacity 0.17 cu.ft./linear ft.1.27 gal./linear ft.

Custom Large Gutter

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I. COLLECTION COMPONENTS

Gutter ScreensA critical element in any rainwater harvesting system is continual filtration of debris. Your gutter system offers the first opportunity to begin this sequence of filtration by the use of screens at the top of the gutter. Besides providing the first level of filtration, screens will help maintain flow in an area that often is the weak link in the maintenance of a rainwater harvesting system because the inside of gutters are out of reach and thus too often out of mind. These gutter screens are a very inexpensive item for the value given.

A. Leaf ScreenThe most common approach is to provide a 1/4 inch screen on the top of the gutter to catch leaves in a location that is much easier to remove than digging them out of the bottom of the gutter. Leaf screens are usually only necessary in locations with tree overhangs. Screens must be regularly cleaned to be effective. If not maintained, leaf screens can become clogged and prevent rainwater from flowing into the tank. Built-up leaves can decay and harbor bacteria.

B. Debris ScreenThis is a commercially available item consisting of a frame with a relatively fine mesh that fits on the top of the standard gutter. The mesh is fine enough to collect most smaller debris yet does not impede the passage of water. Cleaning is easy because all one has to do is hose off the surface using a high pressure nozzle on a garden hose.

Maintaining Gutter Systems

Maintenance of your gutter system is important. Clean gutter screens before the rainy season and check for overflow during winter storms. Repair leaks and holes and look for low spots or sagging areas.

3. Downspout DivertersDownspout diverters are devices that add to our multiple filtration objective by filtering rainwater while diverting water to the storage. Three types are shown below:

Another approach is a strainer basket in a spherical shape than can slip into the drop outlet of the downspout or a cylinder of rolled screen inserted into the drop outlet. Both of these approaches have the difficulty of not being easy to get to for regular inspection and maintenance.

Another simple inline filtration system consists of a filter sock of nylon mesh than can be installed on the inlet pipe at the storage tank. This will require maintenance and needs to be installed without creating gaps that allow access for animals or insects that are attracted to water.

This downspout diverter has an integral leaf eater inline. Debris is diverter with a comb like device and a mesh screen. The diverter can be manually switched off to allow overflow to con t inue down the downspout to the rain garden.

A downspout filter consists of a PVC or stainless steel cage cut into the spout at a height slightly above the highest water level of the tank. The screen is cut into the shape of a funnel that can be easily removed for inspection and cleaning.

A “leaf eater” is a screened co l lec t ion box a t the interface between the drop outlet and the down spout w h e r e t h e d e b r i s i s concentrated and is easy to reach.

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II. CLEANING COMPONENTS

4. First Flush DevicesWhile gutter screens remove the larger debris such as leaves, twigs and blooms that fall on the roof, a first flush device gives the system a chance to rid itself of smaller contaminates such as dust, pollen and bird and rodent feces. The first flush device routes flow of water from the first rain storm from the catchment surface away from the storage tank. The flushed water can be routed to a planted area.

The volume of rainwater to divert to the first flush systems depends on the number of dry days preceding the storm and the local conditions mentioned earlier. one rule of thumb for first flush diversion is to divert a minimum of 10 gallons for every 1,000 sq. ft. of collection surface.

The simplest first flush device is a PVC or meta standpipe in line with the downspout before the pipe to the storage tank. This standpipe fills with water during a rainfall event and redirects water to the tank after it is full. The standpipe can be drained continuously via a pin hole in the bottom or by leaving the screw closure at the bottom slightly loose.

A simple homemade first flush device can be various lengths depending on the diameter of pipe used and amount of diverted water desired. If you use a 3” diameter pipe, 33” will hold one gallon. A 4” pipe will hold the same amount with only 18” of length and so on.

There are now severa l commercial first flush devices available. The dependable ball and seat system works with a floating ball that seals the flush chamber after the chamber fills. This simple system is automatic and does not rely on mechanical parts or manual intervention except for occasional cleaning of settled debris in the chamber.

Roof WashersA more elaborate commercially available inline cleaning system is called the “roof washer.” It is placed just ahead of the storage tank, filters small debris for potable systems and also for systems using drip irrigation. Roof washers consist of a tank, usually between 30-50 gallon capacity, with leaf strainers and a 30-micron filter.

All roof washers must be cleaned. Without proper maintenance they not only become clogged and restrict the flow of rainwater, but may become breeding grounds for pathogens. The box roof washer is a commercially available component consisting of a fiberglass box with one or two 30-micron canister filters (handling rainwater from 1,500-3,500 square-foot catchments). The box is placed atop a ladder-like stand beside the tank, from which the system owner accesses the box for cleaning via the ladder.

5. Filters

Pot FiltersA pot filter is the simplest rainwater pre-filter and is composed of a flanged plastic tray with a perforated bottom that covers the top of a large basin with a side outlet. A filter pad is placed over the perforations, the pad is covered with gravel, and the outlet is piped to a rainwater tank. Water from a downspout dumps onto the gravel which strains out leaves and coarse debris and then flows through the filter mat which retains solid particles as small as 1/64”. With minimal maintenance, a pot filter can capture and filter 100% of the rainwater from a single residential downspout. Normally pot filters are buried so that the top is flush with the ground surface, but they can be used above ground.

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II. CLEANING COMPONENTS

Basket FiltersA basket filter consists of a large screened filter basket that fits within a plastic filter body. Water flows in through a top port, down through the basket, and out through a bottom port. A second port is provided at the top to allow overflow should the filter basket become full. A small basket filter can filter 100% of the rainwater from roofs up to 5,000 square feet, with a larger basket filter all do the rainwater from roofs up to 12,000 square feet. For both, the buried basket system is easily accessible through a removable manhole cover.

Cascade FiltersIn contrast with basket filters, cascade filters do not collect debris, but rather allow it to wash through the filter in order to minimize maintenance. This is achieved at the penalty of lower recovery rates, typically 95% depending on average rainfall intensity. Rainwater flows in through the top port and cascades over a curved, multi-level screened filter element positioned horizontally within a plastic filter body. Filtered water exits through one bottom port; debris is washed down the surface of the filter element and exits through a second bottom port. The filter element, buried underground, is easily accessible through a removable manhole cover, like the pot and basket filters.

Also available are internal cascade filters that fit completely within the access dome of some rainwater tanks. This compact filter is suitable for roofs up to 5,000 square feet.

Vortex FiltersLike cascade filters, vortex filters do not collect debris, but rather allow it to wash through the filter in order to minimize maintenance. Instead of a horizontal filter element, they utilize a vertical filter element. Rainwater flows in through the top port, spins around the circumference of the filter body, and spills into the top of the filter element. A capillary effect draws water through the side walls of the filter element and this filtered water exits through the upper side port. Debris washes down, passes through the open bottom of the filter element, and exits through the lower bottom port. This design requires very little maintenance, but at the penalty of reduced capture efficiency, typically 85% to 90% depending on average rainfall intensity

Pot Filter

Basket Filter

removed for cleaning

CascadeFilter

removed for cleaning

removed for cleaning

Vortex Filter

self-cleaning

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6. Storage TanksStorage tanks sit below the water source, with the inlet lower than the lowest downspout. Tanks should be located as close to supply and demand points as possible and protected from direct sunlight. They can be placed above ground or below ground, though to ease the load on the pump, tanks should be placed as high as practicable. Storage tanks must be opaque, either upon purchase or painted later, to inhibit algae growth. For potable systems, storage tanks must never have been used to store toxic materials. Tanks must be covered, vents screened to discourage mosquitos and animals and those used for potable systems must be accessible for cleaning.

Water runoff should not enter septic system drain-fields, and any tank overflow and drainage should be routed so that it does not affect the foundation of the tanks or any other structures. To ensure a safe water supply, underground tanks should be located at least 50 feet away from animal stables or above-ground application of treated wastewater. If supplemental hauled water might be needed, tank placement should also take into consideration accessibility by a water truck, preferably near a driveway or roadway.

Water weighs just over 8 pounds per gallon, so even a relatively small 1,500- gallon tank will weigh 12,400 pounds. Therefore, tanks should be placed on a stable, level pad. If the bed consists of a stable substrate, a load of sand or pea gravel covering the bed may be sufficient preparation. Otherwise, a concrete pad should be constructed. When the condition of the soil is unknown, enlisting the services of a structural engineer may be in order to ensure the

III. STORAGE COMPONENTS

MetalGalvanized sheet metal tanks are an attractive option for the urban or suburban garden. They are available in sizes from 150 to 2,500 gallons, and are lightweight and easy to relocate. Tanks can be

FiberglassFiberglass tanks are built in standard capacit ies from 50 gallons to 15,000 gallons in both vertical and low-horizontal cylinder configurations. Fiberglass tanks under 1,000 gallons are expensive for their capacity. Tanks for potable use should have a USDA- approved food-grade resin lining and the tank should be opaque to inhibit algae growth. Fiberglass durability has been tested and proven, however, they are vulnerable to wildfires. The fittings on fiberglass tanks are an integral part of the tank, eliminating the potential problem of leaking.

stability of the soil supporting the full cistern weight. The pad or bed should be checked after intense rainfall events.

lined for potable use. Most tanks are corrugated galvanized steel dipped in hot zinc for corrosion resistance. They are lined with a food-grade liner or coated on the inside with epoxy paint. The paint, which also extends the life of the metal, must be FDA- and NSF-approved for potability.

WoodFor aesthetic appeal, a wood tank is a desirable choice for urban and suburban rainwater harvesters. Wood tanks, similar to wood water towers at railroad depots, were historically made of redwood. Modern wood tanks are usually of pine, cedar, or cypress wrapped with steel tension cables, and lined with plastic. The main disadvantage of these tanks is that they shrink when dry and can develop leaks unless continually filled. Even with a liner, the wood will lose structural strength when the wood shrinks. For potable use, a food-grade liner must be used.

1

Photo Credits:1 Beaumont Kansas Water Tower, MadameGraffigny

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III. STORAGE COMPONENTSPolypropylenePolypropylene tanks are commonly sold at farm and ranch supply retailers for all manner of storage uses. Standard tanks must be installed above ground. For buried installation, specially reinforced

In-ground PolypropyleneSome polypropylene tanks are buried for aesthetic or space-saving reasons. However, in-ground tanks are more costly to install because of the cost of excavation and a more heavily reinforced tank. For installation deeper than 2 feet, the walls of the tank must be thicker and sometimes an interior bracing structure must be added. Burying a tank in clay is not recommended because of the expansion/contraction cycles of clay soil.

tanks are necessary to withstand soil expansion and contraction. They are relatively inexpensive and durable, lightweight, and long lasting. Polypropylene tanks are available in capacities from 50 to 10,000 gallons. Low-profile 5,000-gallon polypropylene tanks do not retain paint well, so it is necessary to find off-the- shelf tanks manufactured with opaque plastic. The fitt ings of these tanks are aftermarket modifications. Although easy to plumb, the bulkhead fittings might be subject to leakage.

ConcreteConcrete tanks are either poured in place or prefabricated. Poured-in-place tanks can be integrated into new construction under a patio, or a basement, and their placement is mostly permanent.

Other types of prefabricated concrete tanks include new septic tanks, conduit stood on end, and tanks constructed of concrete blocks. These tanks are fabricated off-site and dropped into place.

Concrete may be prone to cracking and leaking, especially in underground tanks in clay soil. Leaks can be easily repaired although the tank may need to be drained to make the repair. Involving the expertise of a structural engineer to determine the size and spacing of reinforcing steel to match the structural loads of a poured-in-place concrete cistern is highly recommended. A product that repairs leaks in concrete tanks, Xypex, is now also available and approved for potable use. One possible advantage of concrete tanks is a desirable taste imparted to the water by calcium in the concrete being dissolved by the slightly acidic rainwater. For potable systems, it is essential that the interior of the tank be plastered with a high-quality material approved for potable use.

FerrocementFerrocement is a low-cost steel and mortar composite material. For purposes of this manual, GuniteTM and ShotcreteTM type will be classified as ferrocements, which involve application of the concrete and mortar under pressure from a gun. Gunite, often used for swimming pool construction, is a method in which the dry mortar is mixed with water at the nozzle. Shotcrete uses a similar application, but the mixture is a prepared slurry. Both methods are cost-effective for larger storage tanks.

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Customized tanks are increasingly available that are more aesthetically adaptable to match a garden space.

Ferrocement tanks can be customized to a variety of shapes and sizes and therefore can become a compositional element in any landscape.

Photo Credits:2 Underfloor Cistern, Stefan-XP3 Frank Gallagher, www.allindustrialarts.com

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Storage Material Cost Flammable Capacity ModularAvailable

Aboveground (A) Belowground (B)

Metal $$ No ++ Yes A

Fiberglass $$ Yes ++ Yes A/B

Wood $$$ Yes + Yes A

Polypropylene $ Yes + Yes A/B

Concrete & Masonry $$$ No +++ Yes A/B

Ferrocement $ No + No A

Earthen $$ No +++ No A/B

EPDM $$$ Yes +++ Yes A/B

7. Mosquito and Animal ScreensMosquito screens and tight- fitting tank lids prevent mosquito breeding, and keep water-seeking animals from fouling the tank. Screens and filters should be checked and cleaned regularly.

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Specialty TanksWith the wide variety of applications of rainwater harvesting worldwide (including places like Australia

IV. STORAGE COMPONENTS

Tank Maintenance

All tanks eventually build up a sludge layer on the bottom of the tank. It comes from leaves, dirt, and other debris that washes from your roof and is carried by the water into your tank. Because the sludge can be a breeding ground for micro- organisms, this layer needs to be cleaned out regularly. For people who maintain their roofs and gutters, the tank may only need to be cleaned out every three years. For those that are less diligent about maintaining their catchment system, tanks should be cleaned out at least once a year.

+ = less, ++ = more, +++ = most $ = least expensive, $$ = more expensive $$$ = most expensive

Tank Material Comparison TableThe table below compares various storage materials and their relative characteristics.

Ferrocement tanks consist of an armature made from a grid of steel reinforcing rods tied together with wire around which a wire form with closely spaced layers of mesh, such as expanded metal lath is placed. A concrete-sand-water mixture is applied over the form and allowed to cure. It is important to ensure that the ferrocement mix does not contain any toxic constituents. Painting above-ground tanks a light color will help to reflect the sun’s rays, reduce evaporation, and keep the water cool.

Ferrocement structures have commonly been used for water storage construction in developing countries due to low cost and availability of materials. Small cracks and leaks can easily be repaired with a mixture of cement and water applied where wet spots appear on the tank’s exterior. Because walls can be as thin as 1 inch, a ferrocement tank uses less material than concrete tanks, and thus can be less expensive.

where it is mandatory), specialized tanks have been developed that are visually compatible to architectural and landscape situations such as the slimline tank series.

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bacteria, water test kits detect presence of indicator bacteria that come from the intestines. If you have the indicator bacteria in your water that means that you have fecal bacteria in your water, which are very harmful and cause disease.

Rainwater from a properly designed rainwater pre-filtration and storage system can be used without further treatment for landscape irrigation, garden ponds, and most exterior applications. When rainwater is used within buildings, supplemental f i l t ra t i on i s essen t ia l and d is in fec t ion i s recommended. For toilet flushing and clothes washing, a sediment filter will remove suspended solids which can clog and damage valves, and an activated-carbon filter will remove dissolved organic matter which can cause discoloration and odors. For showering, hand washing, or drinking, use a high-intensity ultraviolet sterilizer to kill microorganisms that could cause illness. All filtration and disinfection components should be oversized to maximize performance and minimize maintenance.

Filters used for drinking water are 1-micron filters. These have very tiny holes and are used to remove protozoan cysts like Giardia, which chlorine does not kill. When you are looking for a 1- micron filter look for a filter that says it removes or reduces cysts. This is usually used in addition to the sediment filters.

float switch

9. Pumps, Access Pipe & Auto-Fill Devices

IV. USE COMPONENTS

Float switches and fill valves can be used to fill a tank or engage a pump when the tank has a specific amount of water in it. Although gravity flow can be used for flood irrigation, most other rainwater uses require pumping. Submersible pumps are installed within a rainwater storage tank, but most require a pump controller that cannot be submerged or flooded. Surface pumps are typically installed within a nearby building or pump enclosure. It is important to keep pump housings out of the sun and clear of insects.

Back flow preventers and check valves are important when systems will require an input of fresh water either from a well or a local source. There are two approaches to prevent cross contamination. The first is to provide a 3” air gap at the fresh water inlet. This is an actual space of air that exists when the supply line stops and the water flows through the air before being added to a storage tank. The other strategy is to hard line the additional water source with an inline approved backflow preventer. Municipalities have

UV Sterilizer

Water level indicators can be simple mechanical pulley and counter weight systems or more complex electronic systems. These systems will be tied to your auto-fill device if the tank has a supplemental water supply system. For short water level indicator

The most important reason for water treatment is to kil l dangerous bacteria that may be in the water. Treatment can also improve the color, odor and taste of your water. A treatment program may include a combination of filters, disinfection with bleach and/or boiling water. Most illnesses are caused by fecal

10. Treatment (UV Filters)

8. Water Level Indicators

tanks and rain barrels, a mechanical level indicator will be the most cost effective and easy to calibrate. Pneumatic water level indicators allow for remote sensing and can be installed in below ground situations with water levels up to 8’ deep. Wireless ultrasonic devices can be located at great distances from the tanks (1000 ft.) and can have more sophisticated controls for digitally operating pumps and electric valves. Digital level indicators can work wi th tanks or greater depth, but are not recommended for steel or modular underground tanks because of radio-frequency interference.

many concerns about cross contamination through a siphoning action, so systems require an approved backflow preventer and require inspection yearly for proper function. Charges for inspection services will vary, contact your local authority for more information on inspections and fees.

Images Courtesy conservationtechnology.com

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GLOSSARYappropriate technology applying technology to address problems related to energy use, the water cycle and affordable building at the smallest, most accessible scale possible.

aquifer the underground layer of rock or soil in which groundwater resides. Aquifers are replenished or recharged by surface water percolating through soil. Wells are drilled into aquifers to extract water for human use.

cistern a storage tank or underground reservoir for rainwater.

downspout a vertical pipe that drains water downward from the gutters.

drip irrigation system a watering process in which water flows through tubing and is delivered to plants roots via emitters or sprayers, rate of water flow is adjustable, minimizing water runoff and reducing the amount of water that is lost through evaporation.

drought tolerant ability of a plant to survive with little water.

erosion control techniques prevent soil loss and water pollution, can involve the creation of physical barriers, such as vegetation or rock, to absorb the erosive potential of wind or water.

evaporation process of liquid water becoming a vapor.

filtration process of filtering, especially the process of passing a liquid or gas through a filter in order to remove solid particles.

gravity flow use of gravity as opposed to a pump to move a liquid such as water.

greywater / graywater / gray water is water that has been used in the house and comes from bathroom sinks, shower, baths and washing machines.

groundwater water that occupies the pores and crevices of rock and soil beneath the earth's surface.

gutter channel along a roof’s edge to catch and direct stormwater.

hydrologic cycle the natural sequence through which water passes through the atmosphere as water vapor, precipitates to earth and returns to teh atmosphere through evaporation.

impervious material that does not allow water or other liquids to pass through.

infiltration movement of water through the soil surface into the soil.

irrigation systems key component to any landscape, can be fed from municipal water sources, wells and even better water catchment systems. Using rainwater as a primary irrigation source is a sustainable way to grow a healthy landscape and helps with overall water conservation.

nonpoint source pollution contamination of a body of water from a number of sources and locations.

potable "Drinking water" or potable water is water of sufficiently high quality that can be safely consumed or used domestically.

percolation the movement of water through the soil to the water table.

permeable ability of water or other liquids to pass through a surface.

pervious pavement driveways, walkways and patios made with gravel, crushed stone, open paving blocks, or special porous concrete to allow water infiltration.

point source pollution single, identifiable, localized source of contamination.

pollutant any substance in air, water, or soil that may be harmful to the health of humans or other living things or may harm the environment.

rainbarrel container used to collect and store rainwater.

rain-garden a planted depression that allows rainwater to be absorbed and soak into the ground.

rainwater harvesting process of collecting and storing rainwater or stormwater for beneficial use.

recharge process by which groundwater is absorbed into the zone of saturation.

run-off something that drains or flows off, as with rain that flows off the land.

soil composed of gravel, sand, silt, clay, organic matter, gases, and liquid.

stormwater run-off rainwater that hits the ground and flows over the earth’s surface.

surface water water that collects on the ground or in a stream, river, lake, wetland, or ocean. Shallow trough between two areas of higher ground.

watershed area of land that sheds water and directs it downhill to a particular watercourse or point.

xeriscape environmental design of land using various methods to minimize the need for supplemental water use such as using drought-tolerant plants, mulch, and efficient irrigation to create sustainable landscapes.

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RAINWATER HARVESTING PRODUCTS & RESOURCES

down to –30°F, highly durable, available from 1,000 to 3,000 gallons, with custom offerings up to 200,000 gallons.

Rainwater HOG (Corte Madera, California; rainwaterhog.com): modular rainwater storage tank for use in tight spaces like under decks, against houses, or even within walls, made from food-grade virgin polyethylene, each module holds 47.6 gallons. Tanks can serve as thermal storage for passive solar heating systems.

Jay R. Smith (Montgomery, Alabama; jrsmith.com): systems and components, seven pre-packaged systems, with the smallest designed for roof areas up to 1,600 ft2 and the largest serving roofs up to 5,500 ft2.

Snyder Industries (Lincoln, Nebraska; snydernet.com): Rain Captor line, rotationally molded HDPE tanks for above-ground (300–5,000 gallon) or below-ground (575–2,500 gallon) installations.

Tank Town (Dripping Springs, Texas; rainwatercollection.com): Tanks are either fiberglass (5,000- to 40,000-gallon capacity) or lined steel (9,900- to 65,600-gallon capacity), Eliminator first-flush storage tank that is designed to hold the first-flush rainwater that may be too contaminated for potable use but is appropriate for other uses, including compost tea. Produces its own line of bottled water- licensed drinking water from harvested rainwater.

Water Cont ro l Corpora t ion (Ramsey, M inneso ta ; watercontrolinc.com): storing water from a commercial building’s drainage system and using that water for such non-potable applications as landscape irrigation, toilet flushing, and cooling tower and boiler make-up. Storage tanks can be polyethylene, fiberglass, or lined galvanized steel up to 60,000 gallons in capacity. Disinfection with ozone, UV, reverse osmosis, or chemical treatment.

W a t e r F i l t r a t i o n C o m p a n y ( M a r i e t t a , O h i o ; waterfiltrationcompany.com): filtration and treatment of surface water sources such as ponds, lakes, and springs. Filtering Roofwasher that installs between the downspout and the tank to remove dirt and debris from water collected from a roof and floating cistern filter, which reduces the final filtration loads.

Watertronics (Hartland, Wisconsin; watertronics.com) : SkyHarvester line of custom-designed and -engineered systems for commercial rooftop and parking-lot applications. Systems designed for 3,000 gallons to 1 million gallons or more.

Xylem (White Plains, New York; completewatersystems.com) : Flowtronex line of water pumps for landscape, rainwater, and other low-head applications.

Yaktek Industries (www.yaktek.com.au, or U.S. distributor The Rainwater Store; therainwaterstore.com): manufacturer of simple tank level indicators, pulley-and-counterweight systems that show the water level on the outside of the tank.

Aquadra Systems (Edmonds, Washington; distributed by raintankdepot.com): modular tanks made from 100% post-consumer-recycled, linear low-density polyethylene (LLDPE), components for connecting several tanks together, and brackets for securing them to walls.

Aquascape (St. Charles, Illinois; rainxchange.com): below-ground storage of rainwater or stormwater with the unusual feature of allowing use of that stored water in landscape features, such as fountains and ponds. Storage capacity is created using AquaBlox module crates that interlock to create large cisterns made watertight with EPDM liners.

BlueScope Water (San Marcos, Texas; bluescopewater.com): site-fabricated steel tanks with polymer-composite (Aqualiner) potable-water-rated liners in sizes from 10,000 to 65,000 gallons, tanks are available from 1,000 to 5,000 gallons.

BRAE (Oakboro, North Carolina; braewater.com): components for integrated systems for residential and commercial applications. Systems available for both potable and non-potable uses, especially irrigation.

Bushman (Australian company, U.S. operations in Temecula, California; bushmanusa.com) above-ground polyethylene tanks for rainwater collection ranging in size from 60 to 2,825 gallons. Slimline tanks, ranging in size from 130 to 620 gallons, have a thinner profile to fit against walls, wide range of components.

C o n s e r v a t i o n Te c h n o l o g y ( B a l t i m o r e , M a r y l a n d ; conservationtechnology.com): wide range of rubber and plastic materials for water and air-flow management, systems and components, including pre-filtration, first-flush diverters, tanks, level indicators, pumps, and water purification.

Invisible Structures (Golden, Colorado; invisiblestructures.com): Rainstore3 system for underground storage of rainwater or stormwater runoff from parking lots, modular system is made from 100% recycled HDPE or polypropylene, large storage volumes can be achieved.

Loomis Tank Center (ArroyoGrande, California; loomistank.com) distributes and re-sells a wide range of tanks used in rainwater harvesting systems. It offers fiberglass, HDPE, and galvanized steel tanks from ten retail stores in the Southwest and through 40 manufacturing partnerships in 25 states.

Rain Harvesting Pty Ltd (Australian company, U.S. distribution from Aurora, Illinois; rainharvesting.com): product developers, full line of products, including filtering rain heads with debris filtration, first-flush diverters, tank level monitors, tank overflow outlets, and complete systems.

Rainwater Collection Solutions (Alpharetta, Georgia; rainwaterpillow.com): Rainwater Pillow, an affordable, fabric rainwater storage vessel made of a polyester scrim coated on both sides with PVC, the pillows are flexible, resistant to freezing

American Rainwater Catchment Systems Associationwww.arcsa-usa.org

Hardscapes: Patios and DrivewaysGreenBuildingAdvisor.comhttp://www.greenbuildingadvisor.com/green-basics/hardscapes-patios-and-driveways-0

Harvesting, Storing, and Treating Rainwater for Domestic Indoor UseBy Texas Commission on Environmental Qualityhttp://rainwaterharvesting.tamu.edu/drinking/gi-366_2021994.pdf

Harvesting Rainwater for Landscape UseBy University of Arizona Cooperative Extensionhttp://cals.arizona.edu/pubs/water/az1344.pdf

Natural Yard Care GuideBy Seattle Public Utilitieshttp://www.seattle.gov/util/Services/Yard/Natural_Lawn_&_Garden_Care/Natural_Yard_Care/index.asp

Rainwater Harvesting for Drylands and Beyond By Brad Landcaster http://www.harvestingrainwater.com/

Rain Gardens: A How-to Manual for HomeownersBy City of San Luis Obispohttp://clean-water.uwex.edu/pubs/pdf/home.rgmanual.pdf

Rain Barrel Guidehttp://www.rainbarrelguide.com/

Texas Manual on Rainwater HarvestingBy Texas Water Development Boardhttp://www.twdb.state.tx.us/publications/reports/RainwaterHarvestingManual_3rdedition.pdf

Slow it, Spread it. Sink it. A Homeowner’s Guide to Greening Stormwater RunoffBy Resource Conservation District of Santa Cruz Countyhttp://www.rcdsantacruz.org/media/brochures/pdf/HomeDrainageGuide.v25.pdf

Arroyo Grande(805) 473-5426www.arroyogrande.org

AtascaderoPublic Works(805) 461-5000www.atascadero.org

Grover BeachCommunity Development Department(805) 473-4520www.grover.org

Morro BayCity of Morro Bay - Public Services(805) 772-6261www.morro-bay.ca.us

Paso Robles(805) 237-3850www.prcity.com

Pismo Beach(805) 773-4656www.pismobeach.org

City of San Luis ObispoCommunity Development Department(805) 781-7530(805) 781-7274www.ci.san-luis-obispo.ca.us

San Luis Obispo CountyPlanning & Building(805) 781-5600www.sloplanning.orgPublic Works(805) 781-5252Public Health(805) 781-5500

City of Santa BarbaraBuilding & Safety(805) 564-5485

A watershed is a network of streams, creeks and ground water systems, which drain rainfall and other freshwater from the land into the ocean, an estuary or a river. Every square inch of land is a part of one watershed or another.

Whether you live on a farm, on the coast, in the woods or even in the desert, you live in a watershed. Everyone lives in a watershed, as all lands drain rainfall to one body of water or another. The watershed can be a source of sediment and pollution. As rainwater drains from our yards, hillsides and streets it carries pollution with it. Think twice before you dump cleaners, paint, oil and other chemicals on your yard, in the storm drain or in the street.

SLO Green Buildwww.slogreenbuild.orgproudly partners with the following municipalities. Please contact your city or county building department for questions, guidance and permitting.