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Thread: Best way to splice double walled water lines

  1. #1
    DIY Junior Member leak_chaser's Avatar
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    Default Best way to splice double walled water lines

    Hi all,

    I have a water leak in an underground waterline running to an older house. The leak is about 100 gallons per day. The line is about 1500 feet long. The water line is 3/4 inch thin wall PVC inside a 1 inch thin wall PVC. Burial depth is about 18-24 inches.

    So far I have been unable to find a leak by looking for a wet spot or listening for a hissing sound. If all else fails, I will have to cut the line in two, cap it and see if it still leaks at the meter. That will tell me which half of the line is leaking. Then I will have to do this with the bad half again to locate a bad quarter. And so on until I get close enough to the leak.

    Which brings me to my question. What is the best/quickest/most efficient way to cut the line, cap it and then splice it back together, seeing that the line is double walled?

    Thanks.

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    Moderator & Master Plumber hj's Avatar
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    quote; Which brings me to my question. What is the best/quickest/most efficient way to cut the line, cap it and then splice it back together, seeing that the line is double walled?

    There is no "good way". IT was an idiotic idea to use thin wall PVC for the water line in the first place. Then it was even worse to put it inside another PVC line. Now, when you have a leak, no matter where it is, it only comes out of one end of the sleeve or the other. Even the conventional methods fo leak locating are useless because of the sleeve, although it MIGHT be found by listening for a sound which is imprecise also because of the sleeve. The smart thing, before you start sectioning the line, would be to dig a new trench and install a proper water pipe.
    Licensed residential and commercial plumber

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    DIY Junior Member leak_chaser's Avatar
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    Putting in a new waterline does sound tempting, but might not be feasible in this case. I will probably try to fix it first.

    So how would you go about splicing a line like that if you had to do it? What is a good way to cut the outer sleeve back without damaging the inner pipe?

    Also, should I install some PVC ball valves while I have the line cut, in case I ever have to do this again? Or is it just asking for more trouble? I would just bury the valves without a box or anything.

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    Forum Admin, Expert Plumber Terry's Avatar
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    The line is about 1500 feet long.
    So it should have been at least a 1-1/2" water service line.

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    Moderator & Master Plumber hj's Avatar
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    I would cut the out pipe using a knife heated red hot to melt through it. Cut around the pipe first then make longitudinal cuts to separate it into two pieces. You will have to make up to seven cuts depending on how close the first one is to the break, and hopefully there is only one break. A ball valve, tee, and cap would allow you to repeat the process when another leak occurs, and it will leak again, so do not bury the ball valves.
    Licensed residential and commercial plumber

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    DIY Junior Member leak_chaser's Avatar
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    Thanks. By tee and cap you mean building a sort of a valve access box, correct? It is not part of the plumbing? Would it damage anything if I simply covered the ball valve and marked the location really good? Maybe even put a piece of steel there to use with a metal detector?

    What are my chances of being able to pull the old 3/4 inch pipe out of the 1 inch sleeve and replacing it with some other pipe, maybe pex? I don't mind the flow restriction too much on this one. I guess you never know until you try. There might be too much sediment in between them by now.

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    DIY Senior Member dj2's Avatar
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    Quote: "Putting in a new waterline does sound tempting, but might not be feasible in this case".

    May you tell us why?

    It may be the only and the least expensive LONG TERM solution to your problem.

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    DIY Junior Member leak_chaser's Avatar
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    The water line runs within a foot or less (I am guessing) of the neighbor's water line for maybe 800 feet. The line is not marked. Lots of big trees - big roots. I do not want to tear up the neighbor's waterline.

    The line also crosses a county road.

    Lots of rock close to surface in this general area will make burial a challenge. Supposedly I could follow the old line route, but it may require a lot of hand digging.

    The line may or may not run under some concrete - a sort of a parking area.

    I would sooner not handle the line replacement at this time, or at least minimize how much I replace.

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    Moderator & Master Plumber hj's Avatar
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    quote; What are my chances of being able to pull the old 3/4 inch pipe out of the 1 inch sleeve

    Actually, I don't know how they installed it in a 1" sleeve because it would have had to had couplings every 20 feet and a 3/4" coupling is almost the same size as a 1" pipe so it should not have fit inside it. IF the pipe is not a "tight fit" inside the sleeve and it is a straight pipe, then it should slide out fairly easily. "fairly easily" being a relative term for a 1500' foot pipe.
    Licensed residential and commercial plumber

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    DIY Senior Member craigpump's Avatar
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    Have you heard of Hydrophones? They are like headphones with cups that are placed on the ground along a water line to locate leaks underground.

    They MIGHT help locate your leak.

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    DIY Senior Member bluebinky's Avatar
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    I'm usually wrong about these things -- But, are you sure there are really two pipes the full length and not just sleeved in key areas like under the road or 1" reduced to 3/4"?

    Also, with thin-wall PVC, you could probably cut a short section out of both and then probably just peel back the outer pipe after a couple of passes lengthwise with a utility knife.

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    Moderator & Master Plumber hj's Avatar
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    A hydrophone MIGHT help to locate the lead depending on the depth and the attenuation caused by an outer sleeve filled with water due to the leak.
    Licensed residential and commercial plumber

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