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Thread: TP valve

  1. #1

    Default TP valve

    My TP valve started leaking recently, a little at first then all the time, so I replaced it. Now the new valve weeps after using a fair amount of hot water.

    I've read some threads about needing an expansion tank to resolve this sort of issue, but want to make sure this is my problem. I'm wondering why I need one now after 14 years without.

    Any help would be greatly appreciated.

    Rainierguy


    T&P Valve looking at two sides.
    Last edited by Terry; 04-24-2009 at 10:26 AM.

  2. #2
    Master Plumber Redwood's Avatar
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    Default

    There are 2 reasons why a properly performing T&P valve would leak,

    "T" = Temperature. If the temperature exceeds 210 Degrees F it will open.

    "P" = Pressure. If the pressure exceeds 150 PSI. it will open. This may be caused by high supplied pressure in which case a pressure reducing valve needs to be installed or, replaced. And, or, an expansion tank need to be installed or, replaced.

    This is a critical safety Item and it would be wise to consider the services of a licensed plumber.
    Watch this video... click here!

  3. #3
    Moderator & Master Plumber hj's Avatar
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    Default T&p

    Unless you have a closed system and the seepage IS due to thermal expansion, an expansion tank would either be useless or merely cover up the real problem.

  4. #4

    Default T & p

    Thanks for the replies.

    Looks like it is time to call a pro, don't want to blow up my home because I can sweat pipes and adding hardware without knowing the root cause isn't a good way of solve problems. It will be interesting to learn what has changed in my plumbing to cause the temperature and pressure valve to leak after hot water usage. I'm sure it will be a no brainer for an experienced plumber.

    rainierguy

  5. #5
    TROJAN WORLDWIDE SALES RP MACPLUMB 777's Avatar
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    Default T 7 p valve

    Most likely your water supplier upped your water pressure to
    meet demand, new construction ? New project ??

    This doesn't have to be on your street it could be anywhere in the same area where you get your water from,

    they normally do not inform home owners when they raise the street pressure,

    so yes you need a thermal expansion tank installed a.s.a.p.
    To protect your family, your house, and your water heater warranty
    and also a prv. If you do not already have have one

    MACPLUMB 777

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  6. #6
    Forum Admin, Expert Plumber Terry's Avatar
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    Default

    If the tank T&P started acting up,
    It could be a problem with the tank, thermostats, or elements
    Or it could be that something changed with the public water supply
    Sometimes a new water meter will be installed with a check valve.

  7. #7

    Default Pressure

    A change in city water pressure sounds very likely in light of the new multimillion dollar treatment plant under construction in the city. I would imagine they need more water than before.

    I'll have to call the city utilities and verify.

    I appreciate all the experienced input!

    Thanks

  8. #8
    Plumber jimbo's Avatar
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    Bottom line......get a pressure guage...about $10 at the hardware store, and see what the pressure in your house is...both static, and shortly after running a lot of hot water to kick on the heater.

  9. #9
    Moderator & Master Plumber hj's Avatar
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    Default T&p

    You describe an expansion pressure build up, but without more information we do not know if your installation could have one. That is the reason that you need more information before installing one.

  10. #10

    Default Pressures

    Put a pressure gauge on my line and got 60 psi with tap open 80 psi with tap closed and got 150 psi after running WH out. The T&P valve opened obviously at 150 psi.

    The house was not build with a expansion tank 16 years ago, and I cannot find a pressure reducing (regulating) valve in the house but the meter has something on it but I can't identify.

    Is an expansion tank and PRV needed?

  11. #11
    Plumber Cass's Avatar
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    Where I am located I would install a Watts 25 AUB Z3, a Watts #7 double check valve and an expansion tank sized to your water heater and set 1-2 #s lower than what you set your water pressure at.

  12. #12
    Moderator & Master Plumber hj's Avatar
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    Default valve

    80 psi, regardless of whether it is city or reduced pressure is proper. Something is creating a closed system, so you do need an expansion tank.

  13. #13

    Default

    Thanks for all the very helpful replies, I now understand the basics of my problem and what needs to be done to fix it. Still curious as what has changed and created a closed system, maybe the city can shed some light on that one.

    Great input, thanks for the time!

  14. #14
    TROJAN WORLDWIDE SALES RP MACPLUMB 777's Avatar
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    Default Water heater t&p valve

    That new piece at the water meter is a one way check valve ! !
    That is what is causing your thermal expansion
    use to be when your water heater was running the excess pressure would push back into the city main ! !

    This check valve is required by the E. P. A. To prevent your possible water containments from mixing with city water ! ! ! !

    At 80 psi you do not need a prv at this time but you do need a thermal expansion tank and a
    new t & p valve installed A. S. A. P.
    Be sure to have tank mounted on the cold water side between the shut off and the top of the heater

    MACPLUMB 777

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    35 YEAR MASTER PLUMBER, HEATING, ELECTRIC, DRAINS, FIRE SPRINKLERS, WATER HEATER
    AND BOILERS SINCE JAN, 1989

    281-706-1631 7 DYS A WEEK SALES AND TECH. SUPPORT
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  15. #15
    Plumber Cass's Avatar
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    Out here we remove them and install the Watts #7 in place of it.

    We remove them because after a while they start to rattle and it becomes very annoying.

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