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Thread: What would you do in this situation ?

  1. #1
    DIY Member kstuart's Avatar
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    Default What would you do in this situation ?

    This is a question for professional plumbers only, please thanks.

    Suppose a home with an attached garage, and the gas water heater is in a closet in the garage.

    One morning, the resident finds about a half gallon of water on the garage floor, that has seeped out from the bottom of the water heater closet. The hot and cold lines to the water heater disappear in the back wall of the closet. The temp-pressure relief valve is piped into a side wall of the water heater closet, and exits that wall at a point just outside the closet onto a point over a sheet of linoleum next to the water heater closet, and the top of the linoleum seems dry. The interior of the water heater closet seems dry and the exterior of the water heater seems dry. The water heater sits in a pan which seems dry.

    With every water appliance unused for ten minutes, the water meter does not move at all.

    The resident mops up, but every time they check (every 4-6 hours), there is more water.

    The water heater was installed about 18 months ago ( immediately prior to putting the house for sale, which took 9 months during which the house was vacant ).

    As a plumber, how do you proceed ?

  2. #2
    Master Plumber Redwood's Avatar
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    I would suspect the T&P is discharging from thermal expansion...

  3. #3
    DIY Member kstuart's Avatar
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    Quote Originally Posted by Redwood View Post
    I would suspect the T&P is discharging from thermal expansion...
    1 - Do you mean that the T&P is defective ?

    2 - What about the linoleum being dry under the T&P's discharge pipe ?

  4. #4
    In the Trades Wally Hays's Avatar
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    It's me. I sneak in there about 2:00 am and pour a cup of water on the floor.

    Naaaaaaaa. It's probably what Red said. Thermal expansion.
    Perception is 3/4 of reality

  5. #5
    Plumber jimbo's Avatar
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    You have answered the basic questions, so now it is more a Dick Tracy issue. Someone is almost just going to have to be there to see it happen.

    If you haven't already, get a stong flashlight and some dry tissues, and poke all around the base of the wall of the clost, and all around the overhead area, looking for signs of wet.

  6. #6
    Master Plumber Redwood's Avatar
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    If it was a leaking pipe it would be a constant leak.
    It's not the water heater cause the pan is dry.
    That pretty much says its the T&P Discharging from thermal expansion.
    The reason the floor appears to be dry under the T&P discharge is probably because the floor directly under it is a high spot.

    Run a good amount of hot water so the water heater starts reheating shut off the water and don't run any water hot or, cold, then go watch the T&P start dripping.

    The T&P if it drips isn't bad it's just doing its job and you need a thermal expansion tank installed.

  7. #7
    DIY Member kstuart's Avatar
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    Can a thermal expansion tank be installed in the same place in the system previously occupied by a water softener (which was replaced with a pipe) ?

  8. #8
    In the Trades Wally Hays's Avatar
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    anywhere on the cold water line
    Perception is 3/4 of reality

  9. #9
    DIY Member kstuart's Avatar
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    Quote Originally Posted by Redwood View Post
    The T&P if it drips isn't bad it's just doing its job and you need a thermal expansion tank installed.
    In this case, the city water department states that there is no check valve or back-flow preventer in the water meter. So, unless I am not understanding this correctly, then this is an "open system" and so a thermal expansion tank is normally not needed.

  10. #10
    Master Plumber Redwood's Avatar
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    Do you have a pressure reducing valve?


  11. #11
    Nuclear Engineer nukeman's Avatar
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    ... or perhaps a check valve leftover from where the water softener was installed?

    It would be a good idea to see what the pressure of the system is doing to see if you may be hitting the setpoint for the T&P.

    Another possibility is that there is a pinhole leak in the pipe after it goes into the wall. May be slow enough to not show up on the meter, but enough to accumulate after a couple hours. Have you checked for soft spots in the drywall?

  12. #12
    DIY Member kstuart's Avatar
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    Quote Originally Posted by Redwood View Post
    Do you have a pressure reducing valve?
    Where would this typically be found in the installation ?

    I do not think there is one in this case.
    Last edited by kstuart; 08-03-2010 at 05:12 PM.

  13. #13
    Master Plumber Redwood's Avatar
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    It depends largely on where you live...
    Some places they might be out side on an underground meter box, Others they might be in a basement or crawlspace with the meter, sometimes in tha garage or, a utility room where the meter is located.

    Generally it is new=ar the meter wherever that is located but, it may not always be...

  14. #14

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    How to eliminate the T&P as a possible source of the problem is to simply place a cup directly under the T&P discharge point and wait to see if it collects water. If it doesn't collect water you have eliminated the T&P as the problem.

    The simplest way is the best way and I am not a plumber.

  15. #15
    DIY Member kstuart's Avatar
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    I have noticed that you can get a hose-bib pressure gauge for under $10. It seems that a simple test would be to simply hook one to the drain valve, open it and cause the heater to cycle on.
    ...
    Also, while there are certainly correct reasons for the relief valve to release water, isn't it also possible for the relief valve to be defective ?

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