� ~ ~j air connection and the pipe. Air may beadded through quick-coupling valves, but

.~~ . --:....=..=-~ _ vyeathe~-matic's Don Cooper caution~ thatair cornrng out of an air compressor IS hotenough to damage plastic piping adjacentto the valve.• Locate a 250-cfm or larger air compres-sor (two 125s will do) with a hose and fastenit to your air connections.• Close all valves that could permit water toflow from the irrigated area back into thewater source.• Start the compressor and slowly openthe air connection valve. Do not permit theair pressure to drop below 40-50 psi or theair mass will not move the water properly.On the other hand, excessively high pres-sure can damage pipe and fittings. Mostlarge irrigation systems are designed tooperate at approximately 120 psi at thesource and 80 psi at the heads. Some pipeand fitting manufacturers will not honorwarranties if their products are damaged byimproper winterization.• Select one branch of irrigation piping andopen a group of valves in series. nearest thewater supply. The concentrated high veloc-ity of the air will blow most of the water outof the pipe within a few minutes. When airinstead of water comes out of the heads,shut off the valve to those heads. Do notpermit air to blow through the heads formore than a few seconds or damage mayresult.

Automatic valves, whether electric orhydraulic, open quickly but close slowly.This shut-down time may range betweenfive and 30 seconds. You want the next setof valves to open before the first set closesto prevent pressure from backing up in thesystem. You can instruct the controller toshut down the first set of valves and thenopen the next set of valves as long as youstay within the shut-down period.

Proceed from the source downstreamuntil all of the valves have been opened, thesprinklers have discharged air, and youhave reached the end of the pipe, or anemergency gate valve in the event of a looppipe system. Operate the valves severaltimes so air can replace the water in theoperating parts of the valves.

By controlling the number of valves open,you control the pressure in the line. If thepressure drops below 40 psi, shut offseveral valves. Restart them when the airpressure has recovered.

It is desirable to have a drain or quick-coupling valve on both sides of an emer-gency shut-off valve if all of the water is tobe removed from that line.• Select the second branch of piping andrepeat the previous step, from the source tothe end. Continue the same process untilall branches have been blown.• At the low points in the piping, the airblew past the water, and the water has nowreturned to the low points by gravity. This iswhere the drain valves should be.

With the pipe under air pressure, crackthe drain valve, until all air and no water

continued on page 22

November, 1988 21

1~!"iE;WinterizingIrrigation SystemsProcedures Thai Avoid ProblemsAs managers of high-use recreational

facilities realize the futility of main-taining turfgrass without irrigation, all

types of systems are being installed, fromthe hottest regions of the country to thecoldest.

Irrigation provides a reliable, consistentlevel of playability for turf during periods ofdrought or irregular rainfall. Today there areno boundaries for irrigation - and sportsturf maintenance is changing as a result.

The vital role of irrigation for recreationalturf has also prompted parks, schools, golfcourses, universities, resorts and stadiumsthat already have irrigation systems to con-vert from manual to automatic control, addsophisticated pump stations, and upgradesprinkler heads.

An investment in irrigation goes beyonddesign and installation. Regular main-tenance is critical, in order to preserve theoperational design of the system from yearto year. Advances in controllers have elimi-nated much of the labor involved in operat-ing irrigation systems. However, controllershave not replaced the human eye when itcomes to troubleshooting.

Even though most of an irrigation systemis out of sight, it should not be out ofmind ... especially during the winter. Notonly can freezing temperatures turn waterinto an enemy, procedures used to removewater from the system can damage compo-nents if the turf manager is not careful.Equally delicate is the process of recharg-ing the system in the spring.

The simplest explanation of an irrigationsystem is a series of interlinked containersfull of water. Pressure exerted on the waterat the source pushes it through pipes tovalves that hold the water in chambers.Upon opening, the valve allows the pres-sure from the source to force water throughmore pipes to the sprinkler heads for distri-bution.

All components are designed to hold andmove water within a certain pressure rangeand rate of flow. When conditions exceedthese ranges, the pipe, fittings, valves andheads are all in danger. That is why irriga-tion system designers go to great lengths toselect components and provide extensivespecifications and details for installation.

When water freezes, it expands. If it is

confined as it freezes, the water will exceedthe burst strength of irrigation components,including those made of metal.

For this reason, any portion of an irriga-tion system below the frost line must bedrained in the fall. This process is termedwinterization. If properly done, it takes justa few hours and removes water from allcomponents susceptible to freezing duringthe winter.

Irrigation systems, especially those in thecolder regions of the country, should beinstalled with drainage in mind. Large sys-tems need to be drained or blown out onesection at a time. Emergency shut-off valvesenable you to isolate one section fromanother. Pipe in each section should slopeto low point{s), where drain valves areinstalled in gravel sumps.

A system without drains or graded pipe-lines is far harder to drain than one installedwith drainage in mind. Yet even a systemwith adequate emergency gate valves,drain valves, and pitched piping will not sur-vive poor drainage procedures.

To help avoid such costly failures, weconsulted with specialists in winterizing attwo irrigation manufacturers, Buckner ofFresno, CA and Weather-matic/Telsco ofDallas, TX. Their "inside information"figuratively puts you within the pipe itself.

When draining an irrigation system, con-sider yourself as an air mass crawlinginside the pipe and pushing a ball the sizeof the inside diameter of the pipe to force allthe water ahead of you. The water willremain in front of you until you provide anopening - a sprinkler, quick-coupling valve,or drain valve-to let the water escape fromthe pipe.

You must always look back to see thatyou have not forced any water behind you,as might happen in a loop pipe system, orwhen not starting the drainage process atthe water source.

The following drainage procedure,offered by Buckner, will deal with a properlydesigned and installed system, and shouldshow the need for adequate drainage pro-visions.

• Install two or more one-inch or largerair connections in the water-supply dis-charge pipe, with a gate valve between the

Winterizingcontinued from page 21comes out of the valve. Close the drainvalve and proceed to all drains on theproperty, following the same closing proce-dure with each.

The closed drains will prevent gravel fromthe drain wells, and surface water from rainor a thaw, from entering the system over thewinter months. Spring turn-on is alsoexpedited by not having to make the roundsto close each drain valve.• Repeat the procedure from the fifth step("Select one branch," etc.) on each branchto verify that all air and no water is dis-charged from the sprinklers.• Drain all gate valves, pressure-reducingvalves, check valves, backflow preventers,pump volutes, pressure gauges, and pipingin the pumphouse.

In closing their list of procedural pointers,the Buckner people point out that gravitydrainage of an irrigation system can also bevery successful. Patience is necessary-aswell as a good understanding of the pipesize, water volume, and infiltration rate.However, drainage with air is usually fasterand more effective for the typical installa-tion, they advise.

Cooper, product manager and technicalservices manager for Weather-matic, con-ducts many irrigation service seminarsacross the United States and in Canada."Basically, when you talk about winteriza-tion, you have to talk in terms of specific

areas of the country, as procedures varyaccording to climate," he points out.

Discussing winterization procedures inthe first of four north-to-south climaticzones, Cooper says, "In the northern part ofthe country, basically on a line that goesfrom Colorado north and Montana eastthrough Michigan and all the way to NewYork, systems are winterized to a point thatthey're completely evacuated of water:'

He continues, "Blowing out, to use thetrade term, is done with an air compressorthat injects air into the system till the wateris completely evacuated. It's a very simpleprocess - if done properly.

"If not done properly, a lot of damage canbe incurred to the system," he warns, "par-ticularly where rotary heads are used-andgear drives in particular. So let's talk for amoment about gear drives.

"The impetus for rotation comes from animpeller. Water flowing across the impellercauses it to turn. Through a gear reduction,the rotation speed of the impeller isreduced to about a two- to three-minuterevolution at the nozzle. Depending on themanufacturer of the gear drive, the impellerspeeds will generally be somewhere in the1,ODD-rpm range."

However, he observes, if the impellers areturned on air rather than water, the rotationspeed increases dramatically. The bearingsthat the impeller rides on are not designedfor that type of operation. If the air move-ment is kept going through the heads for a

prolonged period of time, damage canoccur to the impeller bearings. A commonterminology for this is "burning thebearings:'

How long is too long? "The maximumcycle duration after the first head starts toblow air should be no more than 30seconds to one minute," Cooper empha-sizes. Therefore he recommends usingshort multiple cycles for blowing the systemout. "One person should operate the con-troller while others observe what's going onat each head or drain valve. By usingradios, the people in the field can let theperson at the controller know when headsstart to blow air." Another option would be toinstall remote-control devices to run thecontrollers from the field. Someone shouldalso keep a constant watch on the airpressure.

By using multiple cycles, he explains, theimpellers and impeller bearings are notstressed, as they would be with one con-tinuous cycle of evacuation. In most smallinstitutional systems, he advises, the sys-tem can be completely evacuated in aboutthree cycles.

If manual drains are available, once thesystem has been evacuated they should beopened and left open. This procedure isrecommended by Cooper for all types ofirrigation equipment. Of course, thesevalves should be located in such a way thatwater does not collect at the valve opening

continued on page 24

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Winterizingcontinued from page 22and reenter the system.

Automatic drain valves can simplify mat-ters. One example is the King Drain whichcloses when the pressure exceeds 10 psi.As long as the system is pressurized withwater or air, the valve remains closed. Itopens when the pressure drops below 10psi to drain water that collects in low spotsso freezing won't damage the pipes. A filterand back-flow valve built into the drain pre-vent debris from entering the system. Thesevalves allow for winter drainage andeliminate the process of opening and clos-ing drain valves in the fall and spring.

Gard Craw, spokesman for Hunter Indus-tries, a manufacturer of gear-drive heads,says that pressure should be watched at alltimes during blow-out. "Some people thinkthat if they raise the pressure the job getsdone faster," says Craw. "All you need isabout 40 psi and you shouldn't go abovethat:'

"As we travel further south across thecountry," Cooper continues, "winterizationbecomes simply a case of draining themains and laterals through the use of drainvalves.

"The one thing demanding particularattention in these instances would be anybackflow-prevention device set abovegrade-above ground level," Cooperadvises. "Depending on the winter's

severity in your area, special attention willneed to be paid to these units to make surethey are drained.

"As we progress further south, winteriza-tion may simply consist of assuring that thesystem does not operate during an extremecold snap. Where system operation isallowed during the winter, one of the primemethods to prevent watering during such acold snap would be the use of a freeze-stat.This item is simply a temperature gaugewith a switch, or else a temperatu re-sensitive switch. It would preclude systemoperation once the temperature drops to 40degrees or less."

These items can be purchased preset ata specific temperature, or they can bebought with the temperature as an adjusta-ble feature.

"As we proceed south, basically to theCaribbean, the last temperature extremewould require virtually no winterization,"Cooper continues. "In Florida they very sel-dom winterize. Even here, in certain parts ofTexas, we seldom winterize. This is partic-ularly true of south Texas.

"So basically there are four strata of win-terization within the United States. Most ofthe winterization provisions are made atinstallation by the contractor. By this wemean that if you're going to use air evacu-ation, an entryway into the system has to be'plumped' into that system during instal-lation.

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"One thing is mandatory when installingautomatic drains: They must be installed atthe low point of the line being drained, toassure that complete drainage will occur.Automatic drains need good gravel sumps.

"Manual drains also need good gravelsumps-and access to manual drainsneeds to be built into the system at the timeof installation, with attention being paid tograde changes," says Cooper.

"One more place where caution needs tobe used is this: When evacuating with air,do not over-pressure the irrigation system.Too often, during evacuation of the system,people pay more attention to speed than tothe care of the system itself'

When this happens, Cooper emphasizes,the problems that occur during turn-on orrestart the following spring can be tremen-dous, due to damaged equipment-notonly the irrigation equipment, such assprinkler heads and valves, but damage tothe piping itself.

"The reason I make this statement is that,unlike water, air is tremendously compres-sive," he explains. "And, as a result, pres-sure surges two or three times that of theoriginating pressure can be built up in thesystem. In most cases, an irrigation systemis not designed to handle these pressures:'

Cooper adds, "One of the main concernsmost service people have, as far as win-terizing an irrigation system is concerned,is 'What do we do with the controller?'

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"As a rule of thumb, it is best if the con-troller is kept operating. Irrigation con-trollers are designed to be operated 24hours a day, 365 days a year. By operatingthe controllers, the operatingcomponents-gears, bushings, bearings,etc. - in electro-mechanical controllers arekept from obtaining a 'set.'

"In electronic controllers, the circuit com-ponents are kept active and fresh, and thesurge protection is kept functional," saysCooper. "Additionally, the heat generated bythe transformer helps to keep the conden-sation that would otherwise occur to aminimum.

"The main point to remember is that thevalves must be precluded from operating.Most controllers have a switch that breaksthe output voltage to the valves. It is notadvisable to operate the solenoids on thevalves dry-that is, with no water in thevalve."

Some irrigation systems have moisture-sensing equipment installed above groundthat is used to preclude automatic operationif enough rainfall occurs. "When winteriz-ing," Cooper warns, "remember to protectthese devices in addition to the remainderof the system. If these sensors have col-lected moisture and a freeze occurs, theyare more than likely going to be damaged:'

All the precautions that are vital to win-terizing are just as important when adrained system is recharged. Water flowsconsiderably faster in an empty pipe than in

~ • -- • ~ ....::=-=- •• -==- ..

All the precautions forwinterizing are just as

important when adrained system isrecharged in the

spring.one full of water. You don't just turn on thepump and start opening valves. The systemshould be refilled slowly, in order to get allthe air out of the lines first.

"When a pipe is full of water the designvelocity should be four to five feet persecond," explains Cooper. "In an emptypipe, water can reach a velocity of up to 13feet per second. When the pipe becomesfull and the water velocity is suddenlyreduced to design velocity, a pressuresurge of up to three to four times static pres-sure can be generated at the sprinklerhead. Water hammer, caused when thevelocity of the water is suddenly slowed,can burst heads, pipe, and fittings, causingsevere damage to an irrigation system:'

Cooper suggests turf managers withpump stations use just the jockey pump to

charge the system - and keep as manyvalves open as possible. "It may take eighthours or more to charge a golf course irriga-tion system, but the worst possible thingyou can do is rush it," he warns.

He strongly advises that large irrigationsystems include sufficient filters to removesand and debris. Such material can seri-ously harm components when the system iswinterized. Whenever a pipe is repaired,the system should be flushed by removingdownstream heads to remove any dirt, glueor debris that may have entered the system.

Cooper prefers to keep drain valves openduring the winter, in order to allow moistureentering the system from melting snow andrain to drain out.

"It's not unusual for irrigation heads to beunder water or hidden beneath snow duringthe winter," he remarks. "Some of that wateris going to drain into the heads and down tothe valves and pipe. While a portion of thewater will evaporate, the rest needs some-place to go. Keeping the drain valves open,but protected, will get rid of the water:'

Winterizing is something that turfmanagers should keep in mind throughoutthe year. There is more to irrigation main-tenance than meets the eye, and it's whatyou don't see that can hurt you more thanwhat you can see.

"This may require a little extra effort in thefall," Cooper admits, "but it's better thanreplacing damaged components in thespring." ~

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