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PUBLISHED BY THE NATIONAL ENVIRONMENTAL … · PUBLISHED BY THE NATIONAL ENVIRONMENTAL SERVICES CENTER ... netic tape are not fool-proof, though. ... location and depth of the distribution

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Page 1: PUBLISHED BY THE NATIONAL ENVIRONMENTAL … · PUBLISHED BY THE NATIONAL ENVIRONMENTAL SERVICES CENTER ... netic tape are not fool-proof, though. ... location and depth of the distribution

Don’t Lose Them in the First Place The best way to find your distribution linesis not to lose them in the first place, andthe best way to ensure this is to have anaccurate set of as-built drawings. These aredrawings (computer or hard copy) of thedistribution system as it was constructed,not necessarily as it was designed. “As-built” refers to the fact that things changefrom the design stage to the constructionstage, not necessarily because of baddesign but because unforeseen eventsalways pop-up. The as-built drawings needto reflect these changes—all of them.

The design engineer will usually add anadditional charge if the water system asksfor as-built drawings, but this is moneywell spent. Don’t take the revised drawingsat face value. Always check the drawings,and if you find mistakes, make the engineerfix them. Having someone familiar with thesystem present during construction canhelp the accuracy of the drawings. (See theTech Brief titled “Quality Control inConstruction Projects” in the summer 2005On Tap.)

After all construction is done, make sureyou have at least two copies of the as-builtdrawings: one in a safe place, in case of fireor other disaster, and the other at thesystem office. It’s also not a bad idea tohave a set at the treatment plant. Anytimea section of line is replaced or modified, allcopies of the as-built drawings should beupdated.

PUBLISHED BY THE NATIONAL ENVIRONMENTAL SERVICES CENTER

Locating Distribution LinesBy Zane Satterfield, P. E., NESC Engineering Scientist

Photos by Chris Metzgar, courtesy of Morgantown Utility Board

SummaryFinding water distribution lines can be a daunting task. Fortunately, there are several techniquesfor finding your pipes. This Tech Brief examines as-built drawings, locating devices, geophones,and tapping the expertise of previous employees as useful methods for locating distribution lines.

Download all of our Tech Briefs at

www.nesc.wvu.edu/ndwc/ndwc_tb_available.htm

Tracer Wire and Magnetic TapeOver the last 20 years or so, many systemshave opted to put tracer wire or magneticlocation tape on the pipes them-selves. When usedin conjunction withan electronic pipefinder, the job of locat-ing distribution linesbecomes much easier.In fact, some of theseelectronic locaters willwork on metallic pipewithout tracer wire ormagnetic tape.Electronic locatersare discussed inmore detail below.

Tracer wire and mag-netic tape are not fool-proof, though. Not allpipes are metallic or the line may be too bigto induce enough electromagnetic field forthe locator to pick up. If this is the situa-tion, you may be able to first find thesmaller branch lines and narrow the loca-tion of the main trunk line down from there.Tracer wire and magnetic tape occasionallyget ripped during back-fill. When this hap-pens, the signal on a locater will stop at thecut and you have to connect on down theline and backtrack and hope that is theonly break. If the signal stops before you getback to other end, you probably haveanother break.

Photo of a spool of tracer wirecourtesy of Pollardwater.com.

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Tracer wire is typically a12-gauge, coated, copperwire with water-tightconnecting splices. Thetracer wire can beinstalled on top of thepipe or on bottom. Theends of the wire come

up at gate valves,water meters, air

release

valves, pump sta-tions, pressure reducerstations, or test stations, whereyou can have a box just for the tracer wire.When running the tracer wire ends up tothe gate valves, put them on the outside ofthe curb box. This way, when turning thevalve with a gate valve tool, the tracer wiredoesn’t get wrapped around the tool andbecome damaged or broken.

“Tracer wire is a good thing when it worksbut usually it only lasts about a year in theground because electrolysis eats it up,” saysChris McAfee, a circuit rider who workswith small systems for the Maryland RuralWater Association. “The biggest problemwith using a locator on metal pipe is gettinga good ground. That is the biggest flaw wesee. Many things can be used as a groundsuch as a street sign or even a fence.Wetting the soil around the ground stakecan help in completing the circuit. Whenyou use a locator, you send an electronicsignal through the pipe and it comes backthrough the ground. Make sure you have agood connection to the pipe and a goodground.”

No clue? No problemAs-built drawings and tracer wire are, ofcourse, an ideal. However, many systemshave neither. How can you locate your dis-tribution lines when this is the case?Three useful methods are: (1)probing, (2) listening with geo-phones, and (3) talking toformer employees.

Probing uses a 1/2” or 5/8” diam-eter, smooth, stainless steel rodapproximately three to four-and-a-half feet long (rounded not pointedon one end). Insulated probes areavailable through most water utility

distributors and providesome protection when work-ing around buried electriclines (some up to 50,000 volts). Probingtakes a little practice because you have tolearn what it sounds like when you come incontact with different pipe materials.Remember not to drive the probe too hardwhen you are close to the line because youcould pierce a light plastic pipe. A handlecan be welded near the top to help turn theprobe back out. To make probing more effi-cient, locate as many water meters, gatevalves, air release valves, or any other thingto narrow down the distribution line searcharea.

Geophones are listening devices similar toyour doctor’s stethoscope but are used forlistening to things in the ground. Open thenearest fire hydrant and use a set of geo-phones. The sound will be louder near thefire hydrant but you should be able tofollow the line out a little way from it. Keepin mind when you open a fire hydrant thatyou could possibly stir up the water result-ing in customer complaints.

This technique might be best done at nightwhen usage is low, allowing some time forthe water to settle. Also don’t forget toaccount for the water in the water lossreport. The water used from the firehydrant would be for maintenance pur-poses, the same as if you were flushing yousystem. If there is no fire hydrant, a watermeter, flushing hydrant, or any valvedoutlet might work.

“Old timers,” or other people who haveworked for the water system in the past canbe a valuable information source. Get intouch with retired or other former workersand pick their brains. Personnel who actu-ally installed the distribution lines mayhave a surprisingly good memory aboutwhere the lines are located.

Photo of magnetic locator tapecourtesy of Pollardwater.com.

Photo of electronic pipe and cablelocators courtesy Metrotech Corp.

TTeecchh BBrriieeff • Locating Distribution Lines, Winter 2006, Vol. 5, Issue 4

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quency, pressure wave car-ried by the fluid in the

pipe. The range of theplastic pipe locatorscan be limited usuallyfrom 250 to 500 feet ineach direction of thehydrant, meter, or sprin-kler.

The Hard WayWhen other methods fail

and you must know thelocation and depth of

the distributionline, you mayhave no choice butto dig. You canoften start diggingwith a backhoe,but to avoid hit-ting the line orother utilities,you will needto shovel tofinish the job.Use the prob-

ing technique discussedabove as you dig to helpavoid line punctures. Ifyour local area or statehas a call-before-you-digprogram, use it. Keep inmind that many of theserequire a three-daynotice before you dig andthat it’s the law in manyplaces.

Electronic LocatorsThere are many elec-tronic locators avail-able. They work bestwhen the system hastracer wire or magneticlocating tape, but somewill work without thetracer wire or magneticlocator tape. Beforeyou buy, shop around.Have the prospectivecompany send a repre-sentative to demon-strate on a hard-to-find linein your distributionsystem, as well as onseveral types and sizesof line. Use lines thatare at a known locationand depth to see howaccurate the instru-ment performs.

Electronic locators havetwo pieces: one to send asignal of some sort andthe other (usually a hand-held device) to pick up thesignal. Electronic locatinginstruments or electronic

pipe finders consistof a portable radio-direction-finderreceiver. The trans-

mitter induces an electromagneticfield into any buried metallicobject within its range. As thereceiver is carried over and acrossa pipe location, the induced elec-tromagnetic field is detected andproduces an audible tone. On some models,both the location and depth of the buriedpipe can be determined.

Electronic plastic pipe locators are alsoavailable as shown in the illustration at thetop of the page. These are expensive, rang-ing from $1,000 to $2,000, without attach-ments for fire hydrants, water meters, orsprinklers. These locators use a low-fre-

There are specific kitsavailable to help finddifferent kinds of waterlines. Illustration courtesyof Pollardwater.com.

NATIONAL ENVIRONMENTAL SERVICES CENTER • 1-800-624-8301 • www.nesc.wvu.edu

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Photo of electronic pipe andcable locators courtesyMetrotech Corp.

Photo of plastic pipe reciever(above and at right) courtesy ofPollardwater.com.

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Once you uncover the distribution line,document its location and depth forfuture reference. Don’t lose it twice. To dothis, measure from the uncovered line toat least two objects that are relativelypermanent, such as a fire hydrant or util-ity pole. Make reference to the power polenumbers or any other details that willhelp find its location in the future. Thesemeasurements are called “tie downs” andyou need at least two measurements totie an object down, preferably at 90degrees from the uncovered water line.The third measurement is an insurancemeasure if one of the objects has beenremoved or is missing when you comeback in the future. If you want, you cantake more measurements for extra insur-ance. Write these measurements down ina surveyor’s field book or on the waterdistribution system’s plans. When youcome back in the future, locate at leasttwo of the designated objects. Measureout based on your notes and make an arc(like using a giant compass). Then, do thesame from one of the other permanentobjects. Where the two arcs intersect isthe location of the previously uncoveredwater line.

An Unconventional WayWhen locating undocumented lines, youmight at least consider divining (alsoknown as witching, doodlebugging, ordowsing). Divining supposedly workswith the magnetic field given off by buriedmetal objects or the water itself. Keep inmind this technique takes practice beforeyou can be proficient at it. Many waterproducts catalogs even sell magnetomaticpipe locators. These are hand-held

devices that have a collapsible antenna90 degrees from the handle. To makeyour own, cut two coat hangers or braz-ing rods to form an “L,” one leg measur-ing 18 to 24 inches and the other six toeight inches. Held at chest level whileslowly walking, the rods should crosswhen passing over a buried object. Thesetechniques will not determine depth ofthe buried object, only the location.

NESC Engineering Scientist Zane Satterfield is a licensedprofessional engineer and previously

worked for the West Virginia Bureauof Public Health, Environmental

Engineering Division.

About the Author

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TTeecchh BBrriieeff • Locating Distribution Lines, Winter 2006, Vol. 5, Issue 4

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An Equal Opportunity/Affirmative Action Institution

Published by The National Environmental Services Center at West Virginia University, P.O. Box 6064, Morgantown, WV 26506-6064

If you would like to receive any or all of our free TechBriefs, send a request with your name, address, itemnumbers, your phone number, and number of copies toinfo@ mail.nesc.wvu.edu.

You also may call NESC at (800) 624-8301.

References:Jesperson, Kathy. 2003. “Searching for

Groundwater with a Stick.” On Tap(Summer). Morgantown, WV: NationalEnvironmental Services Center.

Kerri, Kenneth. 2002. Water DistributionSystem Operation and Maintenance, 4thEdition. California State University,Sacramento College of Engineering andComputer Science, Office of WaterPrograms, in cooperation with theNational Environmental TrainingAssociation.

Lahlou, Zacharia M. 2001. “Tech Brief:Leak Detection and Water Loss Control.”On Tap (Spring). Morgantown, WV:National Environmental Services Center.

Rader, Larry. 2003. “On The Trail of theElusive Water Leak.” On Tap (Summer).Morgantown, WV: NationalEnvironmental Services Center.

Photo of a magnetomatic pipe locator courtesy of Pollardwater.com.