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Fire Water StorageTanks

Inspection, testing and mainte-nance of fire water storage tanksare critical to fire safety. Watertanks provide stored water forfire pumps and fire protection

systems. The primary standard in usein most companies and municipali-ties is NFPA 25, Standard for theInspection, Testing and Maintenanceof Water-Based Fire ProtectionSystems. NFPA 25 establishes mini-mum requirements for the periodicinspection, testing and maintenance

Inspection, testingand maintenanceof fire waterstorage tanksare critical tofire safety.

For a completeTable of Contents,

see page 3

of water-based fire protection sys-tems. It is not an optimum standard.Rather, it is the minimum, and thelevel of action NFPA 25 requires isthe base from which you should startand improve upon to meet your facil-ity’s needs.Many facilities I visit do not have

an adequately documented inspec-tion, maintenance and testing pro-gram in accordance with NFPA 25.Some do not keep written records of

continued on page 27

The third installment of this series focuses on firewater tanks and provides a review of what shouldbe included in a typical self-inspection program

as it relates to tanks.BY WALTER S. BEATTIE, CSP, CFPS, CSHM

PAGE 4INTERVIEWWalter S.Beattie

D

VOLUME 2 • NUMBER 3

�lıneFireA TECHNICAL PUBLICATION OF ASSE’SFIRE PROTECTION PRACTICE SPECIALTY

PAGE 20WATER MISTApplyingNewTechnologyD

PAGE 23CAMPUSFIRE SAFETYEducatingStudentsD

PAGE 25MASSNOTIFICATIONKey SystemFactorsD

Many industrial facilities rely on elevated gravity tanks plus suction tanks and fire pumps for adequate fireprotection water supply.

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inspections, while others conduct limited or no testing.A facility without a documented program does not meetNFPA 25’s intent. The program must include documen-tation. If it is not documented, most authorities havingjurisdiction (AHJs) will be skeptical that the activitieshave been completed.A program that meets the minimums stated in NFPA

25 is an ongoing program, which typically requires week-ly (and sometimes daily) interaction with the systems. Itshould not be a program that is solely carried out by asprinkler contractor.You are ultimately responsible foryour systems.You must familiarize staff with your facili-ty’s systems, and they should know what actions to takein the event of an emergency. It is unlikely that the sprin-kler contractor will be on site at the time of a fire or otheremergency that involves the fire protection systems.The inspection, testing and maintenance of water stor-

age tanks may require that the tank and/or other fire pro-tection systems be taken out of service, resulting in animpairment to the fire protection systems. If the waterstorage tanks(s) are the sole source of fire protection waterto your facilities, an alternate water supply should bearranged while the tanks are out of service. Proper impair-ment handling procedures should be followed during anyimpairment to the fire protection system.

The information and techniques described in this arti-cle are provided for illustration and general informationand may not be appropriate for your specific equipment.Tank installations vary based on tank type, its age andmanufacturer design, so prior to performing testing andmaintenance, refer to information and instructions provid-ed by your fire protection contractors, consultants and themanufacturer of your specific systems and equipment.

SYSTEMS INCLUDED IN NFPA 25NFPA 25 addresses sprinkler, standpipe and hose,

fixed water spray and foam water protection systems. Itcovers the components of these systems, such as privatefire service mains and appurtenances, fire pumps andwater storage tanks, and valves that control system flow.It does not cover residential installations for one- and

two-family dwellings and manufactured homes. Thisarticle focuses on Chapter 9, Water Storage Tanks. Allitems discussed in the previous articles regarding valveinspection and testing, records plans and calculations,impairments to the fire system should be completed.This article discusses items that apply specifically towater storage tanks. NFPA 25 uses NFPA 22, Standardfor Water Tanks for Private Fire Protection, as the basisfor its inspection, testing and maintenance standards. Notall items listed in NFPA 25 are included in this article,and NFPA should always be referenced for the completestandard.As a review, a comprehensive program includes the

following elements:•Inspection.A visual examination of a system to veri-

fy that it appears to be in operating condition and is freeof physical damage.•Testing.A physical trying or operation of a system

or part of a system to ensure or prove that it is function-ing properly, as intended, or to an acceptable standardof operation.•Maintenance. The work performed to repair and/or

maintain equipment in operable condition.Trained in-house staff or a qualified contractor may

perform the service. As with any inspection, mainte-nance and testing program, good recordkeeping isimportant. Written logs should be maintained, and rele-vant results should be retained for future reference orAHJ review. Ultimately, it is the property owner’sresponsibility to ensure that the systems are properlyserviced. Tenants may also want to ensure that the workis completed satisfactorily. Management should reviewcompleted reports and correct deficiencies. An inspectionand testing program is of limited value if identifiedsystem deficiencies are never corrected.

WATER TANKSFire water storage tanks have been

an important feature of industrial fireprotection systems over the last 150years. Elevated gravity tanks weresome of the earliest tanks used andwere once a common sight at indus-trial mill buildings throughout theearly industrial age in the U.S.Insurance underwriters have consid-ered elevated gravity tanks as one ofthe most reliable sources of water forfire protection, and facilities withthem usually receive favorable ratingcredits, which correspond to lowerinsurance premiums.NFPA adopted the original

COVER STORY

Fire Water Storage Tankscontinued from page 1

During an impairment of the water supply to this facility,portable tanks were delivered to the site and connected to thefire pump. Fire protection was maintained in service due toproper impairment handling procedures.

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Wood stave gravitytank on the roof ofa New York Citybuilding.

Standard on Gravity Tanksin 1909. That standard hasevolved into today’s NFPA 22.High-rise buildings have usedelevated gravity tanks and rooftanks for several decadesbecause the public water sup-ply pressure was not adequateto provide sufficient pressureto reach the hose stationsand sprinkler systems ontop floors.Gravity-fed water supplies

do not require a mechanicalmeans to provide pressure tothe fire system. The elevationof the tank takes advantage ofgravity to supply the pressure.One foot of elevation will pro-vide approximately 0.433 psi,and a column of water 2.31 ft

high will produce 1 psi at the base of the column. A gravi-ty tank, which has an elevation of 125 ft will produce astatic pressure of approximately 54 psi at the base of thecolumn or pipe, which runs from the tank to the ground.Another early tank used in mill facilities and high-rise

buildings is the pressure tank. The pressure tank is a pres-sure vessel and is subject to jurisdictional pressure vesselinspections just as boilers and other pressure vessels.Tanks are installed in the building, typically on the topfloor, and filled with water to approximately two-thirdscapacity. Air pressure is applied to the tank to provide theneeded pressure. The pressure must be sufficient to pushall of the water out of the tank while maintaining the nec-

essary residualpressure requiredto supply thesprinkler sys-tems.As fire pumps

became morecommon,ground-level suc-tion tanks wereinstalled as astored watersource. Most ofthese tanks areinstalled at gradeand normallyprovide positivehead on the firepump so thepump need notdraft from thetank. Below-grade tanks usu-

ally includea vertical turbine pump, which extends into the tank.

TANK CONSTRUCTIONTanks may be built of steel, wood, concrete, coated

fabrics or even fiberglass-reinforced plastic tanks.Elevated tanks must be supported by steel or reinforcedconcrete towers. Using these materials, several differentmethods of construction are used. NFPA 22 providesguidance for the installation methods and arrangementof the tank and associated valve arrangements.

TANK INSPECTIONTank inspection

will vary slightlydepending on thetype of tank installedat a facility. NFPA’srequirements shouldbe expanded basedon recommendationsfrom the tank manu-facturer and the fireprotection consultantand contractor. Eachspecific facility situa-tion must be takeninto account whensetting up an tankinspection, testingand maintenanceprogram.The inspection is

generally divided intoexternal and internalworkings of the tank.Conditions on theoutside of the tankmay also provideclues as to the condi-tion of the tank internally. Forinstance, if the water is black orbrown, this may indicate internalcorrosion. Staining on the tankor concrete floors outside of thetank may indicate seepage.

Exterior Tank InspectionsThe water level should be

inspected on a monthly basis.On most tanks, this is as simpleas looking at a sight gauge on theside of the tank. For elevated gravi-ty tanks, there is usually no exteriorsight gauge. An electronic indicatormay be provided, or the manual fillvalve may be opened to fill the tankuntil water begins to flow from the

A steel tankinstalled in thepenthouse of a

high-rise buildingas a gravity tank.Concrete tanks

may also be usedas a gravity tank.

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The floor of this fire pump room also serves as the top of thebelow-grade concrete tank. Two vertical turbine fire pumps are

extended into the tank to supply protection water for thesprinkler systems. The pump in the foreground is driven by a

vertically mounted electric motor. The pump in the backgroundis driven by a horizontal diesel engine with a right angle drive

on the top of the pump.

This is a ground-level suction tanksupplying a fire pump. Note the con-struction of this tank is steel, whichhas been bolted together. This tank islocated in an earthquake-prone area,and foundation bolts have beeninstalled around the tank base tohelp hold it in place during an earth-quake. The tank water level indicatorshows that the tank level is atapproximately 26 ft of the 32 ftof tank height.

The tank water levelindicator is not func-tioning because thecable to the floatinside of the tank hasbecome disconnected.The indicator hasdropped to theground. This is awelded steel tank.

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overflow pipe. NFPA 25 permits the frequency to beextended to quarterly if the water level alarms are con-nected to a constantly attended location. From a practicalmanner, I suggest that the tank water level be inspectedweekly in conjunction with other valve or fire pumpinspections and tests. It usually takes a glance at a gaugeand is not labor-intensive.Air pressure in a pressure tank should be inspected on

a monthly basis. NFPA 25 permits the frequency to beextended to quarterly if the air pressure alarms are con-nected to a constantly attended location. From a practicalstandpoint, I suggest that the tank air pressure be inspectedweekly in conjunction with other valve inspections. It usu-ally takes a glance at a gauge and is not labor-intensive.The air pressure on a pressure tank must remain at the

appropriate level. Too much pressure could lead to a con-dition called air lock, which could occur if both a pressuretank and gravity tank are connected to a common watersupply feeding sprinkler systems. In the event of a firewith sprinkler activation, when the water from the pres-sure tank is exhausted, too much remaining air pressureacting against the check valve of the gravity tank mayhold it shut, preventing the water from flowing from thegravity tank to the operating sprinkler heads.Air lock can be prevented by increasing the volume of

water in the tank, and decreasing the air pressure. When

the tank fully empties, little or no air pressure shouldremain in the tank.Tanks installed in climates with freezing potential

should be provided with heat. Heating systems should beinspected daily during the heating season. NFPA 25 per-mits the frequency to be extended to weekly if the lowwater temperature supervision alarms are connected toa constantly attended location.Water temperature in tanks goes hand in hand with

inspection of the heating systems. Water temperaturesshould be maintained at not less than 40 °F (4.4 °C).The water temperature should be inspected and recordedweekly during the heating season. NFPA 25 permits thefrequency and recording temperatures to be extended tomonthly if low water temperature supervision alarms areconnected to a constantly attended location.I recommend to clients that more frequent checks are

a worthy pursuit, especially if your facility is in a severetemperature region where temperatures may fall below0 °F (-18 °C). During my career, I am aware of two tanksthat froze. One was a gravity tank, the other a ground-levelsuction tank. In the case of the gravity tank, the freezingwater expanded and split the seams of the tank and thepipe column leading from the tank to the ground. Thefreezing condition was noted when the ice began to thawand drip. Due to the extensive damage, the tank was aban-doned and a fire pump and ground-level fire pump suctiontank was installed at substantial cost. Repairs to theground-level tank were less costly but still substantial.On a quarterly basis, the tank exterior, supporting

structure, vents, foundation and catwalks or laddersshould be inspected for signs of obvious damage orweakening. A good set of binoculars is a worthy invest-ment for tall tanks. The area surrounding the tanks andsupporting structure should be inspected at least quarter-ly to ensure that the area is free of trash, debris, brush orother material which could present a fire hazard or resultin accelerated corrosion. The tank and supporting mem-bers should be free of snow and ice accumulation orbuildup. The weight of the ice is a substantial additionalload on the structural members supporting the tank.Coated fabric tanks should be inspected to verify thesupporting ground is free of erosion.Wooden tanks should be inspected annually to verify

the condition of the hoops and grillage. I recommend toclients that this task should be contracted to a reputablefirm experienced in the construction, inspection, testingand maintenance of wooden tanks. Relatively few com-panies exist with competencies to maintain these tanksand fewer who build or rebuild them.The exterior painted, coated or insulated surfaces of

the tank and supporting structures should be inspectedannually. Many companies that own tall gravity tanks relyon contractors experienced in high tank work to completethis task. Unless you have personnel experienced in thistype work and have adequate fall protection equipmentand training, this is typically contracted work. Althoughsome sprinkler contractors perform this work, many will

Failure to maintain adequate heat in a tank during cold weath-er months may lead to catastrophic failure of the tank.

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ANDTANKLININGCO.,

LONGISLANDCITY,NY.USEDWITHPERM

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subcontract this work to others.Unfortunately, this inspection isan overlooked task for far toomany tanks.

Interior Tank InspectionsInternal inspection should be con-

ducted every 3 years for the interiorof steel tanks, which are not providedcorrosion protection. All other tanksshould be inspected on a 5-year basis.Stencil the date and condition resultsof the last internal tank paint job in aconspicuous location, such as at eyelevel near the manway into the tank.NFPA 25 offers specifics on inter-

nal tank inspection, with supportingmaterial in the annex. The tank maybe inspected from underwater, or itmay be drained for the inspection. If

the tank interior is to be inspected from underwater, siltshould first be removed from the floor of the tank. Thetank and auxiliary systems such as the heating systemand components (including piping) and anti-vortex plates(also referred to as “vortex plates”) should be inspected.The tank interior should be inspected for signs of pit-

ting, corrosion, spalling, rot, other forms of deterioration,waste materials and debris, aquatic growth, and local orgeneral failure of interior coating. If any of these condi-tions exist, additional measures should be taken inaccordance with paragraph 9.2.7, which is a drainedinspection and testing of the tank.Tanks with ring-type foundations with sand in the

middle should be inspected for evidence of voids beneaththe steel flooring. This may be noted by looking for dentsor depressions in the tank floor. In addition, walking on

the tank floor and looking for floor buckling will also beidentifiers. If voids are found, grout or other acceptablefill may be injected below the floor to fill them.A contractor may perform the following tests in

a drained steel tank:•Evaluate the tank coating with an adhesion test in

accordance with ASTM D 3359, Standard Test Methodsfor Measuring Adhesion by Tape Test. This test is alsocommonly referred to as the cross-hatch test.•Take dry film thickness measurements at random

locations to determine overall coating thickness.•Take nondestructive ultrasonic readings to evaluate

wall thickness where there is evidence of pitting orcorrosion.•Perform spot wet-sponge test on interior surfaces to

detect pinholes, cracks or other compromises in the coat-ing. Special attention is normally given to sharp edges,such as ladder rungs, nuts and bolts.•Test tank bottoms for metal loss and/or rust on the

underside. Ultrasonic testing is performed where there isevidence of pitting or corrosion. If ultrasonic testing isnot available, an alternative is the removal, visual inspec-tion and replacement of random floor coupons.•Vacuum-box test tanks with flat bottoms at the

bottom seams, per test procedures in NFPA 22.

TESTINGThe tank heating equipment should be tested prior to

the heating system. If provided, low and high water tem-perature alarms should be tested monthly during coldweather months. Low and high water level alarms shouldbe tested semiannually.Pressure gauges should be tested with a calibrated

gauge every 5years. Gauges notaccurate to within3% of the scale ofthe gauge shouldbe recalibrated orreplaced.Level indica-

tors should betested every 5years. Theyshould be accu-rate and shouldmove freely. If atank has a mercu-ry gauge, NFPA25, annex materi-al A.9.3.1, offersthe proper methodto test the gauge.I find that mostmercury-filledequipment atfacilities that I

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This is a vortex plate inside of the firepump suction tank. It prevents a vortex(a swirling funnel, which allows air intothe suction pipe and fire pump). The anti-vortex plate is required equipment in asuction tank. This is a welded steel tank.The floor is constructed of steel panelslaid on fill material. Setting of the fillmaterial can create voids under this steelfloor.

PHOTO COURTESY OF MATRIX RISK CONSULTANTS INC.USED WITH PERMISSION.

Over time, a significant amount of siltand sediment accumulates inside a tank.This material should be removed wheninternal tank maintenance is performed.

PHOTO COURTESY OF MATRIX RISK CONSULTANTS INC.USED WITH PERMISSION.

Low water levelalarm device andlow water temper-ature alarm deviceslocated near thetop of a steel suc-tion tank. The lad-der leads to theroof access port.

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The overflow of a tank is typically a fun-nel attached to a pipe, which extendsthrough the tank wall. This is a welded-steel, ground-level suction tank.

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visit has been removed over the years. All automatic tankfill valves should be tested annually in accordance withthe manufacturer’s instructions. The valve should be acti-vated automatically by lowering the water level in thetank. The refill rate should be measured and recorded.

MAINTENANCE

Tanks should be maintained at the full or appropriatewater level. Hatches and covers should be maintainedin the closed and latched positions. No debris or wastematerials should be allowed to accumulate, and nounwanted or undesirable foreign items should be in thetank. Silt should not be allowed to accumulate in thetank. Any foreign body has the potential of being trans-ported into the underground fire main system or into thesprinkler system piping. Obstructions in sprinkler sys-tems can prevent the sprinklers from operating properlyduring a fire, and once introduced into the sprinklerpiping, are expensive to locate and remove.Embankment-supported coated fabric (ESCF) suction

tanks should also be maintained in accordance with thetank manufacturer’s instructions. Exposed surfaces ofESCF tanks should be cleaned and painted every 2 yearsor in accordance with the manufacturer’s instructions.Automatic tank fill valves should be maintained by

a qualified person following the manufacturer’s instruc-tions and in accordance with the AHJ. Rubber partsshould be replaced in accordance with the manufactur-er’s instructions. Strainers should be cleaned quarterly.Table 9.6.1, Summary of Component Replacement

Action Requirements, identifies specific instructions forwhenever a component in a water storage tank is adjust-

ed, repaired, reconditioned or replaced. These instruc-tions are important to verify that the device is properlyinstalled and operational.If tanks have lightning protection systems, they should

be inspected, tested and maintained in accordance withNFPA780, Standard for the Installation of LightningProtection Systems.

CONCLUSIONFire water storage facilities are a vital portion of your

fire protection system. They should be inspected, main-tained and tested to ensure that an adequate water supplyis available in the event of a fire. Following the proceduresoutlined in NFPA 25 will help ensure that your equipmentwill operate properly when you most need it. �

REFERENCESNational Fire Protection Association (NFPA). (2008).

Standard for the Inspection, Testing, and Maintenanceof Water-Based Fire Protection Systems [NFPA 25].Quincy, MA: Author.NFPA. (2009). Standard for Water Tanks for Private

Fire Protection, 2008 Edition [NFPA 22]. Quincy, MA:Author.

Walter S. Beattie, CSP, CFPS, CSHM, joined the volunteer fireservice in 1969 and remains involved in fire suppression and pro-tection. He has worked in the highly protected risk insurance fieldsince 1979 in various capacities, including senior loss control spe-cialist, HPR technical manager, underwriting special agent andaccount engineer. He is senior consulting engineer, insuranceservice, with Matrix Risk Consultants Inc. in Miamisburg, OH.He was named 2007-08 Fire Protection Branch (now PracticeSpecialty) Safety Professional of the Year Award and is currentlythat group’s Assistant Administrator.

Practice Specialty Officers Elected by Acclamation

The Fire Protection Practice Specialty (FPPS) Nominating Committee nominated Walter S. Beattie, CSP, CFPS,CSHM, as administrator and Gabriel F. Miehl, CSP, CFPS, as assistant administrator.

As required by the Society Operations Guide, the Nominating Committee’s decision was submitted to andapproved by the current FPPS administrator and the Society Nominating and Elections Committee. No otherFPPS member submitted a written petition for nomination by Feb. 15, 2010; therefore, the slate stands assubmitted.

In accordance with Society Operations Guide 11.2, since the nominees were unopposed, Walter Beattie andGabriel Miehl are hereby declared elected by acclamation. Congratulations to these FPPS officers. �