Locating Small Leak in Water Supply System

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by d3b077, Feb 17, 2008.

  1. d3b077

    d3b077 New Member

    Messages:
    1
    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?
  2. patrick88

    patrick88 Plumber

    Messages:
    836
    Location:
    Webster Ma.

    Did you check to make sure any stops are closed fully?
    The connection your using for testing is water tight also.
  3. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
    2,714
    Location:
    Central Florida
    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.
  4. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
    2,714
    Location:
    Central Florida
    Does anybody have a secret formula or product for detecting leaks that works better than Dawn or kids' bubble-blowing stuff?
  5. Redwood

    Redwood Master Plumber

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    Location:
    Connecticut
    Yup, I've got one!

    looky here...http://www.grainger.com/Grainger/wwg/productIndex.shtml?L2=Ultrasonic&operator=prodIndexRefinementSearch&originalValue=Leak+Detector&L1=Leak+Detectors%2C

    [​IMG]

    $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: Feb 17, 2008
  6. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
    2,714
    Location:
    Central Florida
    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. Redwood

    Redwood Master Plumber

    Messages:
    7,452
    Location:
    Connecticut
    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!
  8. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    How long did it take to learn to use it(learning curve) or had you worked with them in the past?
  9. Redwood

    Redwood Master Plumber

    Messages:
    7,452
    Location:
    Connecticut
    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: Feb 18, 2008
  10. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    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. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,519
    Location:
    Cave Creek, Arizona
    leak

    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. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
    2,714
    Location:
    Central Florida
    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. Herk

    Herk Plumber

    Messages:
    547
    Location:
    S.E. Idaho
    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.
  14. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
    2,714
    Location:
    Central Florida
    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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