0262 1762/03 © 2003 Elsevier Ltd. All rights reserved WORLD PUMPS October 20032

In the USA and many othercountries, the practice ofproviding perforated drainage

piping at the footing of buildingfoundations has been commonplacefor nearly a century. Removing groundwater in this manner is essential forlong-term foundation stability and tominimize the potential for stormwater infiltration into below-groundbasements, cellars and, moreimportantly, finished living spaces(Figure 1). Additionally, removingthis water prevents hydraulic pressureunder the cement floor slab,preventing cracking and waterpermeation that otherwise will occur.

AC pump solutions

For those fortunate to have houses onhills or high ground, or for those withmunicipal storm drains buried deepbeneath streets, this drain-pipedstorm water discharges by gravity flowto lower ground or to city-providedstorm-water systems. For others onflatter terrain and for those withoutmunicipal storm sewers, AC electricmotor-driven sump pumps areinstalled in a sump pit below thebasement floor to eject this stormwater to a municipal storm drain orover the top of the foundation andaway from the building.

These AC electric motor-drivenpumps are typically verticalcentrifugal designs, ranging from 0.25to 0.75 hp. Most are fully submersible,oil-filled designs installed entirelywithin the sump pit. Pedestal pumpsare also applied with moreconventional, air-cooled AC motors,typically mounted 2-4 feet (0.7–1.3m) above the sump cover and shaftconnected to a vertical centrifugalpump installed in the sump pit. Aslong as AC power is available, thesepumps provide a good solution,cycling on demand via an electricalfloat switch.

In the USA, homeowners experiencepower outages once or twice a year onaverage. Long-duration outagesexceeding 1–2 hours occur on theaverage once every 2–3 years (Figure2). In older communities, with maturetrees in close proximity to overheadpower lines, outages of both short andlong duration can occur several timesa year. Unfortunately, most of theseoutages occur during severe stormswith high winds, lightening andheavy rains, often coinciding withhigh water flow rates to the sump pit.Power outages as short as 20 minutesor less can result in sump overflow.Power outages of longer duration,more than 1–2 hours or even days, canspell disaster for a homeowner, withthousands of gallons of storm waterbacking up from the sump and intothe basement of the house, below-ground family room, gardenapartment, or English basement. For

Innovative pump solution tostorm water backup

The backup of storm water into basements and other underground building spaces duringpower outages of any duration presents costly problems for homeowners. To address thislongstanding issue, US inventor Michael Ostrowski has designed and patented a new high-efficiency water-driven sump pump that utilizes the power available in the pressure andflow provided by the local municipal water utility. Here he discusses the marketbackground and existing attempts to solve the problem before providing details of thenew design and its performance.

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Figure 1. Cellars andunderground livingspaces are at riskfrom infiltration bystorm water.

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those with unfinished basements,often used for storage, work shops andplay areas, the problem can benonetheless significant in terms ofdamage and clean up. For those withonly AC-powered sump pumps and nostand-by generator, any outage withrainfall can result in significant stormwater backup.

Secondary DCsystems

A partial remedy has emerged – thefitting of a second battery-poweredDC motor driven sump pump. As longas the battery remains well chargedand in good condition, this additionalDC pump and battery is partiallyeffective for addressing the shortduration outages. Actual hours ofoperation for these DC pump andbattery packages are a function ofbattery amp-hour capacity, pumpsize/horsepower rating, motor andcentrifugal pump efficiency, the ‘dutycycle’, flow rate, and head of stormwater that must be ejected. As the DCmotor operates and the batterydischarges, motor speed and/or torquediminishes, reducing pump flow rateand/or pressure performance,eventually fully discharging with lossof pump operation and storm waterbackup. To protect the DC motor,most manufacturers of these batteryDC pump systems provide anelectronic cut-off control, openingthe circuit to the DC motor before thebattery is entirely discharged. So evenfor those with a battery-powered DCpump, storm water backup oftenoccurs.

According to major homeownerinsurance companies in the USA, thecost of both covered and uncovereddamages due to storm water backup isUS$1.5-2 billion annually, despite themany battery DC pump secondarysystems installed to date. In additionto the significant damage andmonetary cost of storm water backup,below-ground flooding of homes andother buildings represents significantrisk of injury or death for the peopleinvolved – from falls on wet surfaces,or electrocution as homeowners try toresolve power problems, operate

rental or portable generators, rentalAC or portable pumps and othermake-shift approaches for removingbacked-up storm water.

More recently, additional factors havecome to the attention of manyinsurance carriers and homeownersalike such as the risk of moisturedamage and high humidity levelsthroughout the building for longperiods of time, the possibility of mouldcontamination, health risk and thelong-term damage to the entiredwelling. The worst case in somehomes, especially in oldercommunities, is for storm-water systemsand raw sewage systems to be ‘cross-connected’ either in the home itself orvia municipal systems overburdenedduring heavy rains. The result for thehomeowner during a power outage canbe raw sewage backup through thestorm water sump or underground floordrains. The human toll in terms offinancial loss, damaged personal effects,difficult and often messy clean up, aswell as lost time, and the surprise natureof the problem remains in the minds ofany homeowner who has experiencedthis problem.

Stand-by generators

The option for a stand-by, engine-

driven generator with automatic start-up has been available for many years.In addition to the generator itself, anautomatic transfer switch is needed toprotect power utility workers from therisk of ‘back feed’ during outages, sothat repairs can be safely made ontheir system. Due to the relativelyhigh installed cost of $5000–$15 000for a small generator set, fewer than1% of homes in the USA have suchunits. Although potentially promisinglong term, fuel cells for homeownersas a lower cost alternative to engine-driven generators are not expected inthe near future.

What other possible energy sourcescould solve this problem? Beyondbattery DC pumps and generator sets,what other high reliability, unlimitedduration power sources could be used?Steam engines, engine-driven pumps?Unfortunately cost, complexity, noise,emissions, the need to auto start, andsafety remain as negatives as withstand-by generators. Compressed aircylinders? Unfortunately, suchcompressed air storage would have tobe too large and costly overall. Solar,wind? Probably not available ‘24-7-365’. Thermoelectric/thermionicconverters and sodium sulfur batteriesfrom the defence and aerospaceindustry – fine for spacecraft and

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Figure 2. Power outages occur once or twice a year in the USA, mostly during heavy rain, lightening and highwinds. On average, outages exceeding 1-2 hours occur once every 2-3 years.

0262 1762/03 © 2003 Elsevier Ltd. All rights reserved WORLD PUMPS October 20034

ocean buoys but, unfortunately, toocostly and potentially dangerous for atypical homeowner.

Water-poweredtechnology – highefficiency, simpledesign

Hydroelectric power – the conversionof moving or falling water into shafthorsepower via a water turbine to runa generator – traces back to da Vinci’swater wheel itself, converting themomentum and energy of movingwater into shaft torque andhorsepower. As with centrifugalpumps, hydro-turbine efficienciestypically range between 40–60% withlosses due to fluid turbulence,momentum loss needed to changefluid direction/velocity, and fluidfriction at high velocities withcomponent surfaces.

During the past 50 years, thehydraulics industry has developedlinear and rotary, positive-displacement actuators to provideanother means of converting fluidpower into mechanical work, but nowwith far better efficiencies. Forincompressible fluids, such as

hydraulic fluid, positive displacementactuators and pumps can approachnearly 100% efficiency in convertingmechanical work/energy [force ×distance (F.dS) or torque × angle(T.dŁ)] into fluid energy [pressure ×change in volume (P.dV) or volume ×change in pressure (V.dP)], and backagain. Hydrostatic/hydraulic, positivedisplacement pumps with fluid power,‘hydraulic’ motor packages andincompressible hydraulic fluids canachieve very high system efficiencieswith good design practices.

To better understand the presentinvention, consider the workings ofhydraulic linear actuators and positivedisplacement, piston pumps, and thatwater, like hydraulic oil, is a nearlyincompressible fluid. This new designis essentially a ‘double acting’ water-driven linear actuator coupled with alinear ‘double acting’ positivedisplacement piston pump, both withvery high energy conversionefficiencies.

Principles ofoperation

As shown in the Figure 3, municipalwater pressure and flow enter the

upper actuator controlled by aflow valve that is designed soas to be either ‘full on’ or’ fulloff ’. The float itself is fittedwith adjustable stops toprovide for a finite on-offduty cycle, as with the floatswitches found on con-ventional AC motor sumppumps. On-demand, munici-pal water pressure and flowenter the self-reversing watersupply valve, which directsthis flow and pressure streamto alternate sides of thepiston, reversing flow pathsautomatically as pressure risesin either of the chambersabove and below the piston asthe piston hits a stop at eachend of its stroke. The waterremaining in each chamber atthe end of each power strokeis forced out of the actuatoron the alternate stroke, at

lower pressure, to the sump itself, asanitary sewer, or to discharge outsideof the building.

For the case of a 4” diameter actuatorand the typical 30–50 psig watersupply pressure, a nominal 375–625lbf up/down force is transmitted to thelower 8” diameter piston, resulting in7.5–12.5 psig discharge pressure fromthe lower chambers with each stroke,or approximately 17–29 feet (c. 5–9m) of head – more than the 10–12feet of head required in mostapplications. With the 1:2 diameterratio of the upper versus lower pistonsand their 1:4 relationship in areas, the5–6 gallon/min (c. 19-23 l/min) flowrate into the upper actuator results ina 20–24 gallon/min gross dischargeflow rate from the lower pumpchamber, with the device operatingwith a 4” stroke and at approximately23 strokes per minute. In the lowerchamber, four check valves are fitted,and conventional 1.5” diameterpiping to minimize pipe pressure dropand pipe friction losses.

Performance

For the case where the spent water fromthe upper actuator is directed to thesump itself, the net storm waterdischarged is 15–19 gallons/min. Inmost cases, full 20–24 gallon/min pumpperformance will be possible, with thespent actuator water having sufficientpressure remaining to be dischargeddirectly out of the building in parallelwith the ejected storm water or directedto a separate sanitary sewer.

The efficiency of the design will be94–95%. With good design, O-ringand rod seal friction will be limitedto less than 20 lbf or approximately4% of the 375–625 lbf connectingrod force. The only other area ofefficiency loss is in the ports of theself-reversing water supply valvefitted to the upper actuator. Thisefficiency loss will be limited to1–2%. High efficiency is animportant feature of the overalldesign, since the spent waterdelivered to the upper actuator mustultimately be discharged from the

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Figure 3. Conceptfor the pistonversion of thewater-driven sumppump.

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building along with the storm waterejected by the lower piston andchamber. Further, water venturi typedesigns are commercially availablebut, due to their 40–50% efficiency,can consume more water than can beejected, often with rated gross or netdischarges of less than 5 gallons/min,falling far short of the 15–20gallons/min that is typically required.

Design variants

The design shown in Figure 1 anddescribed above is merely oneexample of the many bore sizes, flowrates, stroke lengths andstrokes/minute of an entire family ofthe many dimensional designspossible, with straightforward designrelationships determining componentsizes, pressure and flow rates. Forlarger homes, or commercialbuildings, the entire design can bescaled up in size, theoretically,without limit. For homes with shallowbasements, the upper actuator can besmaller in diameter compared to thediameter of the lower pumpingchamber, to further minimize waterconsumption. As a stand-by pumpoperating only during power outages,water consumption and water cost aretrivial compared to the avoided costof flooding damage.

The patent filings for this invention(US Patent 6527518 and PCT021/30284) include embodiments andclaims for the fitting of diaphragms toeither or both the upper actuator andlower pumping chamber, as shown inFigure 4. Notably, with diaphragms inthe place of both pistons and their O-rings, the friction and efficiency lossnoted previously is eliminated.Diaphragm flexing force will be lessthan 1 lbf for each diaphragm withthis alternative design. Additionally,the cylindrical shape and finishquality on the inside surfaces of bothcylinders become unnecessary, andeither chamber can be shaped insimilar fashion to conventional air-operated diaphragm pumps. Further,the storm water that must be handledmay contain dirt, sand and othercontaminants that are better

accommodated with adiaphragm design for longerlife and minimal or nomaintenance.

So when and where can I buyone? Watch future issues ofWorld Pumps and your localhardware store or plumbingsupply dealer for commerciallaunch announcements. Inthe meantime, try to stay safeand dry when the lights goout!

CONTACTMichael OstrowskiInventor and President,Technology MarketConsultants707 Skokie Blvd., Suite 410Northbrook, IL 60062, USA.Tel: +1 847 205 9656Fax: +1 847 498 5712E-mail:m.ostrowski@tmcchicago.com

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Figure 4. Diaphragm variant of the sump pump shown in Figure 3.