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Thread: Mystery hot water running

  1. #1

    Default Mystery hot water running

    I have a gas hot water heater that, for the last week, has been constantly trying to heat the water (with a normal flame), but I only get warm water throughout the house. There is a slight sound of running water that is loudest behind the shower/tub on the second floor. There is no evidence of water on the ceiling below the shower or anywhere else. When I turn off the water supply to the tank, the sound slowly stops, and the water quickly heats up to normal temp. Each time I need hot water, I must turn on the tank supply, and then off again when finished. The shower-tub control is a Moen 2739A single handle control. Yesterday I replaced the cartridge, thinking that there might be something that was related (It also had a slight drip that is still there with the new cartridge --except when I turn off the water supply to the heater).

    Before I tear into the wall behind the tub, is there any other possibility that there is hot water crossing through the Moen apparatus into the cold water pipes? The heater is not dumping through the relief valve, but it is going somewhere after it leaves the tank output line??


    If the picture of the Moen parts does not show up, go to this Moen URL and click on "STEP 1: View Illustrated Parts Diagram to find the part you need ".
    http://www.moen.com/buymoen/buyparts...D796DD170970E8
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  2. #2
    Plumber BAPlumber's Avatar
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    Default

    sounds like a leak in the hot water piping somewhere in the house. the sound of the leak could transmit itself quite a ways. Is there a bathroom directly below the upstairs bath? is there a crawl space?
    Brent

  3. #3
    Consultant cwhyu2's Avatar
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    Default by pass?

    This is not a pressure balanance faucet.You could have a broken dip tube
    in your w/h a by pass mixes hot with cold.How old is your w/h?
    Last edited by cwhyu2; 08-26-2007 at 02:55 PM.

  4. #4

    Default

    Brent, the 2nd floor bathroom where I hear the sound the loudest is over my garage. I have had some unrelated leaks in the past, and it shows up as a stain on the ceiling sheetrock (nothing yet). There is no other plumbing nearby. There is no useable crawlspace, other than the space between ceiling trusses over the garage. The hot water loss must be substantial since the heater cannot get past minimal warm--about 120 degrees F.

  5. #5

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    CWHYU2, the heater is a Sears Kenmore 8 with a "Roto Swirl" dip tube. I don't see anything to allow water to escape without making a puddle somewhere. It about 6 years old (WAG).

  6. #6
    Plumber jimbo's Avatar
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    Default

    Do you have a recirculating pump on the hot water system? The hot/cold crossover really does not happen unless you have a pump.

    The other possibility is an underslab leak, if you are on a slab. Check for warm spots on the floor anywhere on the first floor.

  7. #7
    Plumber BAPlumber's Avatar
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    You probably have a leak underground. Need to find a plumber who does underground leak detection or a leak detection company.
    Brent

  8. #8
    Consultant cwhyu2's Avatar
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    check this out .Is your washing machine operating properly.
    sometimes if the solinoid valve becomes stuck it can make sound like water
    running through out the whole house.This will cause a by pass.
    With out being there its hard to diagnose.

  9. #9
    Plumber BAPlumber's Avatar
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    Default

    Quote Originally Posted by cwhyu2
    check this out .Is your washing machine operating properly.
    sometimes if the solinoid valve becomes stuck it can make sound like water
    running through out the whole house.This will cause a by pass.
    With out being there its hard to diagnose.
    from what's been said it doesn't sound like this problem has anything to do with a mixing valve or bypass. the hot water is getting out of the system somehow. slab leak.
    Brent

  10. #10

    Default

    No recirculating pump & washing machine is ok. I will now spend the day checking for hot spots in slab. Over time, maybe plants/weeds will start to grow where they didn't before. Is it possible for there to be a higher pressure in the hot water line than in the cold line (due to expansion heating of the water and an anti_back flow check valve)? If so, then some defect in the Moen valve cartridge (o rings or the 2 big rubber gaskets) might allow hot water to be pushed back into the cold line??!!

  11. #11
    Master Plumber master plumber mark's Avatar
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    Talking slab leak

    If the washing machine is not doing a bypass thing

    then most likely you got a slab leak and that is nothing

    but fun fun fun....

    I suggest before you start to tear the floors up,
    you might want to consider seeing if you can re-run the water lines up out of the concrete for both hot and cold..

    it sounds like a lot more work but the hot lin can get you again anytime again.


    becasue once you have one slab leak usually you can
    expect another one ....they usually come in 3


    weigh your options carefully before you get out the
    jackhammer...and pull back the living room carpet.




  12. #12
    Forum Admin, Expert Plumber Terry's Avatar
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    Default

    I'm throwing in a vote for leak under the slab.

  13. #13
    Homeowner geniescience's Avatar
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    how much time does it take, after you turn the water supply to the heater back on, for the temperature of the hot water pipe coming out of the heater to feel only 120 degrees? Instead of real hot.

    David

  14. #14
    Consultant cwhyu2's Avatar
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    Default

    Quote Originally Posted by BAPlumber
    from what's been said it doesn't sound like this problem has anything to do with a mixing valve or bypass. the hot water is getting out of the system somehow. slab leak.
    I did not know it was a slab.But if it is aleak underground on hot water side
    then the pressure and volume may be lower on the hot side.If pressure and
    volume are the same on hot and cold.Then I think dip tube.Regardless of age of w/h.

  15. #15

    Default

    When I turn the water supply back on, there is a 5 second rush of water to refill the tank. At this point, the water was normal hot. Running the water in the sink for 4-5 minutes brought the temp down to about 120 degrees. If there is a leak in the slab, is there a diy test to confirm it other than feeling the concrete for warmth? This is Corpus Christi, Texas, and everything is hot!


    BTW, in a somewhat related subject, When I attempted to replace the cartridge yesterday, it was stuck, as advertised (not). In reading all the posts here and elsewhere, I saw a picture of the tool that is made to remove these cartridges. Years ago, I bought a box of plumbing gadgets at a garage sale for pennies, and lo--there was this odd tool and I had no clue of it's purpose. It was the extractor! See why I ignore my bride's pleas to "throw out all the things that you never use in the garage"? Anyway, most posts indicated that it only removed the inner part of the cartridge and messed up the brass outer part. I put a big washer between the extractor and the Brass housing to keep from bending the housing as I tightened the nut. Also, I didn't bottom out the screw that goes into the valve stem. I didn't move the bar handle, since the tabs that it is meant to turn were long gone from the cartridge. It came out in one piece. The washer has to have an inner hole that is big enough to allow the cartridge to pass through it as we tighten the outer nut (see picture).
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