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Thread: Locating Small Leak in Water Supply System

  1. #1

    Default Locating Small Leak in Water Supply System

    I'm having an impossible time finding a pinhole leak in a residential water supply system. During an air test at 75 psi, the pressure loss is about 5 psi in 30 minutes. Over 14 hours the pressure loss is 30 psi. The lines have been searched numerous times using soap/water to find the leak. No luck.

    All the water supply lines have been replaced with new copper and walls are open. Fittings are primarily sweat fit with a limited number of thread fittings. Ultimate working pressure will be about 50 psi. During construction the only water source available is about 30 psi.

    Your thoughts?

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    Plumber patrick88's Avatar
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    Quote Originally Posted by d3b077 View Post
    I'm having an impossible time finding a pinhole leak in a residential water supply system. During an air test at 75 psi, the pressure loss is about 5 psi in 30 minutes. Over 14 hours the pressure loss is 30 psi. The lines have been searched numerous times using soap/water to find the leak. No luck.

    All the water supply lines have been replaced with new copper and walls are open. Fittings are primarily sweat fit with a limited number of thread fittings. Ultimate working pressure will be about 50 psi. During construction the only water source available is about 30 psi.

    Your thoughts?

    Did you check to make sure any stops are closed fully?
    The connection your using for testing is water tight also.
    I'm just starting to work with an old friend of mine to bring solar electric and hot water systems, wind turbines, Flex Fuel Boilers, batteries, hydroponic gardening, books, pellet grills and more. Also the parts for DIY installation.

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    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    As Patrick said, be sure the leak is not in your testing apparatus. That said, run the pressure up some, and see if the leak becomes more pronounced. I test everything at 100psi for 24 hrs. If the leak persists, see if you can isolate it to a specific section of the plumbing system -- install isolation valve(s) if need be. If all else fails, there are leak location firms out there who use acoustic techniques that are just short of miraculous. They can find a leak under a slab to within an inch or two. With all the plumbing open, this should be a piece of cake. I used an outfit called "Sleuth" in Tampa, but I'm sure there are similar firms all over the country. Most work on an "if we can't find the leak, you don't owe us anything" policy, and charge a couple of hundred bucks if the leak(s) are found.

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    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Quote Originally Posted by d3b077 View Post
    using soap/water to find the leak
    Does anybody have a secret formula or product for detecting leaks that works better than Dawn or kids' bubble-blowing stuff?

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    Master Plumber Redwood's Avatar
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    Yup, I've got one!

    looky here...http://www.grainger.com/Grainger/wwg...k+Detectors%2C



    $400 will have you locating any compressed air leak from 20'-30' away like its screaming at you. I used this type equipment locating compressed air leaks in manufacturing plants. I located and marked over 130 compressed air leaks in a 75,000 sq. ft. manufacturing plant in 1.5 hours. The ultrasonic leak detector picks up the non-linear air flow that occurrs around air leaking under pressure fron a pipe. As little as 10 PSI. can produce detectable leakage.

    You start out at high sensitivity from a distance to see if there are leaks in an area then lower sensitivity to pinpoint the exact joint lowering sensitivity as you approach.

    They had so much leakage they were running out of air capacity while the plant usage peaked. They were considering a larger compressor system. After we fixed all the leaks they had plenty of capacity and we sweeped the plant 2X a year after that to maintain system integrity.
    Last edited by Redwood; 02-17-2008 at 06:04 PM.

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    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Oooh, I'm jealous. I'll bet you could go into the new-construction-leak-detection business and recover the cost of that sucker in a week!

  7. #7
    Master Plumber Redwood's Avatar
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    The first use paid for it! Now its all gravy... It was so much fun doing that plant... I had 3 guys behind me documenting and tagging the leaks... They were running like mad men!

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    Plumber Cass's Avatar
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    How long did it take to learn to use it(learning curve) or had you worked with them in the past?

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    Master Plumber Redwood's Avatar
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    Very little time. All that I did was start out in the room waving it around at high sensitivity then I went in the directions that it alarmed in when pointed in that direction. Lowering the sensitivity as I got close and sweeping in directions to dicern multiple leaks that were in the same area. The multiple leaks was probably the hardest part of it because you have to continue sweeping to make sure your not going by one and the severe leaks can be so loud they cover minor leaks close by so you eventually have to get real close at the lowest sensitivity. Its almost as easy as operating a flashlight in a dark room only your flashlight makes noise and has a dimmer switch.
    Last edited by Redwood; 02-18-2008 at 04:55 AM.

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    Plumber Cass's Avatar
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    Quote Originally Posted by d3b077 View Post
    I'm having an impossible time finding a pinhole leak in a residential water supply system. During an air test at 75 psi, the pressure loss is about 5 psi in 30 minutes. Over 14 hours the pressure loss is 30 psi. The lines have been searched numerous times using soap/water to find the leak. No luck.

    All the water supply lines have been replaced with new copper and walls are open. Fittings are primarily sweat fit with a limited number of thread fittings. Ultimate working pressure will be about 50 psi. During construction the only water source available is about 30 psi.

    Your thoughts?
    If you can fill the system with dyed water using a bucket and transfer pump, then pressurize the system to 100PSI you will find the leak.

    Just using water may work.

  11. #11
    Moderator & Master Plumber hj's Avatar
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    Fill the system with water and look for a wet spot. It doesn't have to be colored water either. If the leak does not appear at the normal pressure THEN add air to pressurize it to 100 psi and look for the drips.

  12. #12
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    I would "color" the water with fluorescein dye. Then go around after dark and use a UV to spot the leaks, which will luminesce. Pretty spectacular. I went to college at a university on a river, where unnamed students would now and then dump some dye into the river and shine a UV light on it. Even more spectacular.

  13. #13

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    When polybutylene pipe first came out, they said they required us to test with high pressure, so I got a hydrostatic pump. It's a hand-pumped thing that you can hook a hose to, then hook it to the waterline. You fill the pipe with water from well or city, then use the hydrostatic pump to bring it up in pressure. I bet you'd see the leaks pretty easily at, say, 120 - 140 psi.

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    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    That's actually a better way to test than air only. Catastrophic failures are much less dramatic but it's a much safer procedure.

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