water main leak detection

[dayexco]

i'm curious what different people use to detect a slow leaking water main that will not expose itself.

 

[surfer-joe]

Usually someone's car breaks into the hole. That happened a lot in Grand Junction, Colorado a few years ago and I still read about similar incidents from time to time elsewhere.

 

[d4c24a]

shhhh

a good ear and a listening stick , Acoustic detection instruments are also extremely efficient

 

[digger242j]

Geophones.

I remember my Dad, (who was with the city Water Department) showing me these things when I was 9 or 10 years old, and letting me fool around with them. He swore by them.

I was halfway surprised to still be able to find them. (The link and picture are just from one of the Google results I got, and don't constitute an endorsement of the particular brand.)http://www.pollardwater.com/pages_product/P512geophone.asp

 

[jperfect]

i have used a probing rod and put my ear to it

 

[Dwan Hall]

What Digger posted works for me. I borrowed them from our city water dept.

 

[xcavate77]

we use a metro tech listner. works pretty well but it takes some practice to sort our what you are hearing. you have to shut the equipment down to eliminate some of the background noise. it helped me find a leaky corp stop in about 15 mins after we had been digging for a day and a half. we have even used it to help locate main that couldnt be traced by banging on a valve with a valve key and pinpointing the echo down the line. well worth the money (1200-1500$)

 

[tylermckee]

I found one today on a new 8" line we put in when i saw the hole was full of water. leaking between a T and a valve, flanged connection that got put together in the street so it should have been clean. Don't know what the guy putting it together did.

 

[Machine head]

This is a interesting subject, on my recent site i have been doing mains testing, and the only way we have detected leaks is to isolate inline gate valves 2 miles apart on a 25 mile line, then pump the 2 mile sections till they hold recomended pressure, if pressure drops we walk the line that is being pumped, if the leek is not visable we pump water in the tested main till leak is visible, generaly there will be sinkage or water seeping when leaking. i have never came across these devises you guys have been mentioning. can some one please explain to me how these devices work and how any other available devices may work?
thanks
Machine head

 

[Dwan Hall]

Used an electronic version of the picture posted to find a 1.5 gpm leak in a 10 year old water system yesterday. The owners were going to dig up the complete RV park to find this leak. I went in when no one was around and it was quiet. took about 1/2 hour to narrow the leak down to a stand pipe to a vacant RV site. Results was 15 minutes digging by hand to repair. Saved the park weeks worth of work, ten's of thousand of dollars and the same in restoration. I rented the unit from a local waterline contractor for $65. There is a place in Lost Vega$ that rents it by the week and will send it to you. all you need is a credit card.

 

[Dominion 410]

watermain leak

Slow leaks can be a real pain to locate.I doubt the geophones would detect it.We are required here to have 8' of bury on watermain due to frost and cold winters.That amount of cover does not make it geophone friendly.Even have exposed the main and applied the geophones directly to the pipe to see if we could ballpark a suspect area,with not much luck.I've tried different methods,but the one that worked the quickest and easiest was helium gas. Purged the line of water,by draining a low point or using air.Connect the helium tank(s) to watermain and slowly start to introduce helium gas into the main.A gas detector is needed to locate the leak.The helium will surface right close to the leak.We had a slow leak at an mj fitting and it picked it right up through 8' of fill.The tech just walk along with the detector and basically said X marks the spot.We excavated the area and sure enough that was it.
Have had a few experiences with leaky mains,but thankfully not to many.The odd mj fitting where a bolt was not tightened enough-have switched to electric impact wrenchs since,that seems to have cured those gremlins.Always check the nut on mainstops after opened to make sure they are tight.All bolts on valves.
Just a few suggestions.
Had two leaks because of slag pockets on ductile iron pipe.One was on a 24'' line,2100 foot long with only valves at either end.That was fun,but the manufactuer paid the time on both occasions.

Dominion:canada

 

[rshackleford]

this is a pretty interesting subject. i have worked on project with up to 200 miles of pipeline and have seen some really slow leakers. the worst one was a pvc pipe that had rubbed on the delivery trailer and the water was "misting" out of the rub marks. this was probably a half a cup an minute leak but it was enough to fail a pressure test. to find it we cut the line in half and tested. then cut it in half again. then again. and again. and again.

most of the time a person can drag your feet long enough and a leak will surface. i have not seen anything really great that can help you detect one in pvc pipe. i have tried listening devices but had little luck

i would to see this thread continue to grow.

 

[Dwan Hall]

this is a pretty interesting subject. i have worked on project with up to 200 miles of pipeline and have seen some really slow leakers. the worst one was a pvc pipe that had rubbed on the delivery trailer and the water was "misting" out of the rub marks. this was probably a half a cup an minute leak but it was enough to fail a pressure test. to find it we cut the line in half and tested. then cut it in half again. then again. and again. and again.

most of the time a person can drag your feet long enough and a leak will surface. i have not seen anything really great that can help you detect one in pvc pipe. i have tried listening devices but had little luck

i would to see this thread continue to grow.

On a long 2" line with a sizeable leak we inserted foam pig with a transmiter (Radio detection unit) let it move along till it stoped moving. there was the leakl dug it up and repaired. Took a little work but well worth the effort.

I have done the 1/2, 1/2, 1/2 thing but it is only practical on new uncovered line.
There is a co. here in town for a short stay that uses a puter and listning device. they hook up at 2 locations and can tell you ware inbetween there is a leak. over a city block they uasualy are within 5 or 6 feet of the leak. This co. comes through town once a year on contract with the city and stays here for 1 week. There charge for the weeks worth of work is about $6000. City money well spent.

 

[Dominion 410]

interesting subject

PVC pipe, while more user friendly than ductile iron can be damaged quite easily.Gouges,scratches,scuff marks because of poor pre-install handling can sure make for a bad day in the pressure test department.Have'nt had a leak yet on pvc pipe on account of those reasons to date.The odd leaky saddle or main stop seems to be the only problems we've ever had with pvc watermain.Some manufacturers said their pipe could be direct tapped but never found this a good way to tap services on pvc.Have always used a double bolt style Teck or Robar saddle for tapping.Cutting and isolating sections of line is the surest method to narrow down a leak,imo.Not the cheapest at times,but it's worked the best for me.

I agree,this is a good thread to keep going.


Dominion

 

[PPIC1]

For locationg very small leaks (1 litre or 1/4 gallon per hour) for all types of large diameter pressure pipe including PVC (12" / 300mm and larger) check out the Sahara Leak detection system; http://www.ppic.com/solutions/new_pipelines.shtml or check out the video at http://www.ppic.com/video/sahara.shtml. The sensitive acoustic hydrophone is pulled into place with a pull tape while executing the pressure test and once the leak is located a sensor sends a signal to the surface identifying exactly where the leak is located (marked and noted with GPS). No needless digging is neccessary to try and locate. All that is required is a 2" access point and a pull tape being installed in the pipeline prior to re-pressurinzing. Many contractors have been very pleased with the service, which saves big $$ and allows the completion of the project.

 

[pb777]

If the main is exposed put the brightest light u can find inside and u might see the fracture shine through. if that doesnt work buy a bottle of chalk powder and cover the section of pipe. the water will wash off the chalk were the leak is.

 

[Acivil]

I just always send up a prayer, and start walking the line to see what I can see. Worst leaks I have ever seen have been bad sections of ductile, and seeping gaskets.... both types only leaking over 150 psi on a 200 psi test. MAKE YOU PULL YOUR HAIR OUT! Especially in the winter when you can't tell if its line water or ground water you are looking at. We always meter the amount of water required to bring the line back to test pressure at the end of the test duration... with a little experience, you start to get a feel for the type of leak you have based on the rate of leakage and then start isolating and digging from there. This is by far the most useful thread I have seen on this site. Keep it coming!

 

[EDENBROS]

Leak Detection

There are a couple of low cost methods of finding leaks on buried pipes that will work on most leaks. The first is leak noise correlation using an instrument that 'listens' to the leak noise from 2 sensors placed on the pipe and then computes the leak position. This works very well on metallic pipes, but is less successful on plastic pipes, especially over longer distances.

The second method is Gas Detection, where a safe mixture of 5% Hydrogen / 95% Nitrogen is injected into the pipe and detected above ground with a sensor. This works very well on plastic pipes and small leaks. Obviously, the bigger the pipe diameter and length the greater the volume of gas needed, but in the case of the previously mentioned leak on plastic pipe, the distance could be halved and then gas injected at that point.

For more information, take a look at this link:


http://www.edenbros.com/prodSeCorr08.htm

 

[Ken Wright]

Leak locatind

Perhaps the easiest way to locate leaks that are small and difficult to hear is to use Helium as a tracer gas. It is an inert gas that is easy to get at any welding supply distributer. It is 100% detectable and perhaps the safest compressed gas to work with. That said you will want to purchase or rent a good Helium detector such as the Radiodetection MGD-2002. It is relatively easy to use and can detect leaks as small as 25 ppm. (note a laytex baloon leaks (through its pores) at at between 25 & 500 ppm depending on the quality of the baloon) Not alot of helium. That said it is not necessary to get the pipe to 100% helium, just a reasonable concentration.

for more information on the MGD-2002 and how it is used for leak locating you can contact Radiodetection at (207) 647-9495.

 

[racedaymechanic]

Ive had a few tough ones in the last 30 years, Short of digging up every joint about 20 years ago we had a line that baffled everyone it was about 60 miles from home and all the Foreman made the trip there for a week or so with no luck my turn came, so I thought about it and heres how I found the leaks, I made up a 1/2 inch rod about 8 feet long with a point one one end and a hook on the other, Then I measured 20 feet increments from the gate well and put down a paint mark at each, with a backhoe I put a laborer in the bucket with a small jack hammer and he would hammer the rod down about 5 feet then I would pull it out and move ahead 20 feet, it took about 14 hours to do the sections that were known leakers about 1/2 mile total I think, then I just left line pressure on and came back in the morning, sure enough about 1/4 mile apart we had 2 small Geysers, I dug down and both holes we punched were within 5 feet of the leaky joints, rolled rubbers it was a job done in 0 degree weather