Finding irrigation line leak


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Old 08-11-16, 09:21 AM
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Finding irrigation line leak

I moved into a new-to-me house in December of 2015. In May of this year, I had natural gas line trenched 500 feet up to my house. They cut the irrigation lines in 13 different places (that I know of). They were easy to spot because when I turned the system on, water bubbled up to the surface where the breaches were (they buried the broken lines after "fixing" them with electrical tape - long story). I made all of the repairs (or so I thought) and verified that all 16 zones on the system work.

The house was built in 2011-2012 and has a paved driveway. The driveway had no issues. Over the past few weeks, I noticed an indentation form in the driveway about 2/3s of the way down - right in the middle. It got bigger and bigger. Yesterday I decided to poke at it with the end of a broomstick. Needless to say, it's a big hole now. I was able to dig down through the asphalt, then some stone and ultimately to very wet mud. The soil is being washed away from under the driveway about a foot down. I can only assume that I still have a leak in the irrigation system somewhere. The issue this time is that the water isn't bubbling up making it obvious where the leak is. The closest sprinkler head is about 25 feet away from the sinkhole so I have no idea where to begin looking. I'm also perplexed by the fact that all of the zones work okay. I would think a pressure loss would show by the heads not popping up. Any clever ideas around how to find the leak? I shut the system down to see if the hole stops getting bigger. Everything is covered with new grass now, so I can't really even tell exactly where the construction was anymore.

The only other possibility is an issue with a system of drywells that catch rain runoff from the roof, but I doubt that would cause what I'm seeing here. Plus it's too big of a coincidence that the problem began after the natural gas construction.
 
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Old 08-11-16, 10:02 AM
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Is your house's water supplied by a municipal source or a well? It's possible that you have a leak in the water line to the house.
 
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Old 08-11-16, 10:03 AM
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Electrical tape, I love it LOL. I hope the "long story" took care of that.

A small leak will not affect the pressure enough to prevent the system from working. There are detection devices that can listen for those leaks and help pinpoint where they are. I would start by talking with my water company. They may not provide that service for you, but they would know who could.

Bud
 
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Old 08-11-16, 10:58 AM
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Oh man I never thought of that - I do have city water. Hopefully that's not the case, but on the brighter side that wouldn't be my problem. All of the utilities were marked except the irrigation system because it's not considered a utility and is technically my responsibility per my contract with the gas company. Because the lines are plastic, I couldn't mark them. The contractor verbally told me not to worry about it - they'll fix what they break. They fixed it with electrical tape and other wacky stuff they happened to have in their toolbox and buried it. The long story is that they also hit a septic tank with the backhoe. It was an abandoned one that needed filled. Since it wasn't the gas company's responsibility, I wrote a check to the contractor to fill it with QP. Once I saw the BS they pulled with the sprinkler lines I told them to tear up the check and we would be even. They resisted until I sent them pictures of their handiwork. Case closed (foreman got fired).

So back to the subject at hand. I'm going to check for the obvious first - a couple of the heads are too high. I'm going to make sure they didn't get hit (they're all along the edge of the driveway). Lacking something obvious, I may have to contract with someone that can listen for leaks. In the meantime I'm hoping the driveway stops sinking, meaning it's not my main water line.
 
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Old 08-11-16, 01:11 PM
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You mentioned that all of the leaks you identified and fixed were bubbling to the surface but whatever is leaking now is not. That suggests this leak may be deeper or near disturbed soil where it can drain down instead of bubbling up.

Also, since you repaired many of the breaks you know those are no longer an issue, or hope so. That could leave the remaining leak to be the responsibility of the gas company. A good argument to make them come back or pay for resolving this problem.

My first call would be to the water company. They can listen for the leak and then shut off the water inside your home. If the sound stops then the leak is on your side. If the sound continues then the leak is on their side.

Bud
 
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Old 08-12-16, 06:21 AM
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I checked last night and the water meter isn't running so it's not a leak beyond the meter. The irrigation system's control box is shut off but I left the water valve open. So at least it's holding pressure to the valve outside.

The driveway seems to have stabilized after I shut the irrigation system off. I compressed the gravel that I filled the hole with by running over it a few times with my truck and it hasn't sunken any further. It's rained pretty heavy the past few nights so I think that eliminates a drainage issue.

I found that I could wiggle one of the sprinkler heads just above where the sink hole is. It's definitely still threaded into the fitting at the base but it's loose in the ground making me think a leak is finding its way along that pipe and then potentially down under the driveway. It's one of the lines that was repaired, too. I'm going to dig that one up to see what's going on down there.
 
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Old 08-28-16, 11:20 AM
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Well it's been a couple of weeks with the irrigation system shut off. The driveway has stabilized. I excavated the sprinkler head about 15 feet up hill from the sinkhole, along the edge if the driveway. It was dry. It had a small leak at the base but nothing major. I excavated another, again along the edge of the driveway a bit downhill of the hole and it's fine too. The one uphill of the sinkhole is fed by a line that crosses where they trenched for the gas line. Following this line I'm getting pretty far from the sinkhole, but I guess the water can take just about any path it wants down the hill. The previous owner didn't have any trouble with the sprinkler system so there has to be a break where they excavated. I can still follow the scar in the lawn but I'm not sure where to start digging.
 
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Old 08-28-16, 05:05 PM
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Maybe I missed something, but....you checked your water meter and it is not moving ? Is the meter in the sidewalk by your house...or somewhere else. Is it possible the meter moves so slow that usage is not apparent?
 
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Old 08-28-16, 05:22 PM
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Yes, water can take almost any crazy path underground. It will follow the path of least resistance and show up quite some distance from the source of the leak. Excavations are a good path as the earth is more freshly tilled and the gravel under some driveways can allow it to travel a really great distance.
 
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Old 08-29-16, 06:38 AM
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Yes, I watched the meter in my basement and it doesn't move at all. It has a few different dials, one of which moves very fast with any sort of usage.

And yes, I believe there is a line cut in the trench they dug for the gas line and it's following the gravel under the driveway. When I opened the driveway up, I could see it was running down from above but that still makes it pretty much a needle in a haystack. It was a 500-foot trench along the driveway, torpedo under it about 400 feet up, trench to my front walk about 50 feet, torpedo under the front walk and then into the basement.

My concern is the torpedo under the driveway. They could have hit anything under there. The sinkhole is a good 150 feet down from the torpedo point and around a curve. Not too far uphill from where they went under the driveway, they hit a bundle of sprinkler lines and wires that feed 2 control boxes and some heads in the front yard. I fixed all of that, though. I doubt it's leaking there.

I really don't know where to dig next.
 
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Old 08-29-16, 09:29 AM
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At some point I'd consider abandoning the problem line and just run a new one. As you know it can be very difficult to locate a underground leak. Running a new line may be the simplest solution.
 
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Old 08-29-16, 11:26 AM
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I may ultimately have to do that, but I need to narrow it down. There are 15 zones, each with 4-5 sprinkler heads on it. 10 of the zones are in the front. I can eliminate 5 of them right off the bat: 2 are downhill of the sinkhole and 3 are programmed out (I haven't used those zones yet since I moved in). I can also eliminate the lines that feed the control solenoids since if I turn the main valve on, it feeds all of the zones. The water meter does not run when I turn it on so there's no leak there.

So it has to be one of 5 uphill zones. I guess I can run one a night until the sinkhole starts to sink again.

Here's a pic, The yellow is an approximation of the trench for the gas line. Since sprinkler heads line the driveway, many of the lines that feed them were cut. There are sprinkler heads all over the lawn, too. I fixed them all - all are operational. I don't *think* I have an inoperative zone, which perplexes me. A small loss in pressure causes the heads to not pop up. I don't see any that don't work. The yellow blob in the pic is on the other side of the driveway where they torpedoed under and also where one of the biggest repairs was. The sinkhole is circled at the bottom. I don't know whether I should be looking for something way up top or closer to the sinkhole. There are no other soft spots or sinkholes in the grass or anywhere else.

 
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Old 08-30-16, 06:46 AM
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It is possible that soil got into some of the 3 irrigation lines that are programmed out....and clogged up the valve so it does not close 100%. Just a thought.
 
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Old 08-30-16, 10:43 AM
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Could be. I turned the system back on last night and put it on its regular schedule. I'm hoping that I get some more clues in other areas that would help me identify where the issue lies. Each zone runs for 30 minutes, so if it's a single zone doing it (and I think it is), it must be a significant leak.
 
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Old 08-30-16, 11:40 AM
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I forget all the details but do you see visible water pooling anywhere or is the only clue the sinkhole?
 
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Old 08-30-16, 11:53 AM
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That's the odd part - the only cue is the sinkhole in the driveway. I walked all over the property, paying special attention walking along the trenched area, looking for wet spots or soft spots. There don't appear to be any others.

Looking in the hole in the driveway, I could see that the area that was washed out was pointed pretty much straight up the hill, but that's the only clue I have.

The sprinkler head closest to the sinkhole was draining when the system shut off because it is the last one on the zone on the steep slope. To be safe, I replaced it over the weekend with a new one that has a checkvalve, but I don't think the leak-down would have been enough water to cause that washout.
 
 

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