Equipment/strategies to locate a break in underground PVC piping?

[plowhog]

Somewhere, unknown, is a cracked or broken pipe compromising the pressure in my gravity irrigation system. The piping is 2 feet sub-grade, in well draining loamy soil, so water is not pooling anywhere on the surface. There are also some natural springs in the pastures. That is going to complicate any attempted repair once I find the crack or break.

I have no schematic but know the piping is installed like a Christmas tree-- a 4" main line going up the center, with 1 1/2" lateral lines going to sprinklers both left and right. The darker area in the center of the photo is where the 4" line is. Each lateral line has 3-4 sprinkler risers. I can sight along the risers and pretty well approximate the location of the lateral pipes. There are no shutoff valves. I'm pretty sure the crack or break was caused by an unexpected rapid draining that caused a vacuum to build.

My local rental yard has a pipe inspection device that goes 50' only, to fit in a 4" pipe. More likely I need something that can go 200 feet, with a camera and sonde transmitter, plus fit into a 1 1/2" pipe. Even with 200 ft reach, I'd have to work from both ends toward the middle.

Unless I can find the leak using equipment, I plan to first locate the 4" main pipe, then locate each junction where a lateral pipe connects, then install a ball valve shutoff on that lateral. Then keep repeating until I get pressure back.

At my lowest sprinkler location, I should have 42psi. Maximum I get now is only 20psi. I have used a stethoscope to listen at each sprinkler riser location, and based on what I hear I do have a guess of the general area, maybe also which lateral line might be leaking. But it's only a guess.

I'm not opposed to buying equipment to help find the leak. But $6,500 +/- for a one time repair is hard to justify. I've seen units for half that price but they don't get very good reviews-- plenty of failures of the cheaper units with no parts availability if they do fail.

Any ideas?

 

[PlumCrazy814]

I know some guy that borrowed an infrared camera from work and successfully located underground piping for a septic system.

 

[Snobdds]

Put pressure on the start of that pipe and go start listening for leaks.

 

[grsthegreat]

We use a professional locating company to find broken underground pipes for our association water system. They used some machine that “bumped” or pulsated, the water in the pipes and a piece of equipment that could listen and find where the noise stopped, indicating leak zone. Only problem is, the bumping could theoretically cause other poor fittings to give way……

 

[plowhog]

I considered pressurizing with an air compressor and listening for hissing and/or leaks, but it seems doing that is highly recommended. Something to do with making a bomb out of the pipe.

 

[caver]

They locate broken sewer lines by putting a lawnmower engine in a frame with a small prop that fits perfectly over the nearest manhole. They use industrial grade smoke bombs over the prop intake. Smoke will find its way to house sewer vents but also create a little wisp of smoke if there is a break underground. I saw it in action when I worked for an engineering firm doing a sewer survey. We did the locating and took notes comparing to the city's prints. A smoke crew came behind us a few days later.

 

[hayden]

The water pressure will tell what elevation the top of the water in the pipes is located at. That will be some amount above the leak point, depending on how fast the water is flowing into the system vs flowing out through the leak. If you can cap off the inflows, the level will stabilize right at the leak elevation. From there you will need a transit or other way to accurately figure elevation. If the leak point is below the branch point, then you will know pretty exactly where the leak is located. If it's above the branch point, you won't know which branch has the leak, but you will know where to look on each.

Each PSI of pressure is 2.31 ft of elevation. You need to measure the water pressure as accurately as possible, so get a really good gauge, with a range as close to the expected pressure as possible. So if the pressure is around 15 psi, get a gauge with a range of 20-30 psi, not one that 100 psi. The calculated elevation is the height above wherever you are measuring the pressure. And note that it's the vertical elevation of the leak, not the length down the pipe.

Depending on the distances involved, another way you could do it is with a long hose. Connect one end to an outlet in your irrigation system, and drag the other end of the hose up the waterline. Crack open the hose valve and work your way up and down the pipeline path looking for where the water stops coming out of the hose. Right where the water stops flowing out of the hose is the elevation of your leak.

 

[hslogger]

I hired a leak detection guy from fifty miles away and it was worth it. He charged the system with helium.

 

[dodge man]

They locate broken sewer lines by putting a lawnmower engine in a frame with a small prop that fits perfectly over the nearest manhole. They use industrial grade smoke bombs over the prop intake. Smoke will find its way to house sewer vents but also create a little wisp of smoke if there is a break underground. I saw it in action when I worked for an engineering firm doing a sewer survey. We did the locating and took notes comparing to the city's prints. A smoke crew came behind us a few days later.

I did this several times for work, I did entire towns. I don’t think smoke testing would work in pipes this small.

 

[CalG]

Wait until you are having a dry spell.

Watch how the grass grows green at the leak. ;-)/