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  1. #21
    Join Date
    Aug 2007
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    The Great White North
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    Default Re: New Expansion Tank/T&P Valve Still Leaking

    So to review.....

    40 gallon electric hot water tank

    water pressure from PRV is set to 40 psi

    2 gallon expansion tank installed at cold water supply side of water heater

    air charge for expansion tank is matched to water pressure of 40 psi

    T&P is rated at 150 psi and engages

    ..... sounds like thermostat(s) in water heater are not working and allowing the heating elements to run full on constantly. It's over heating and causing thermo expansion which is also overwhelming the capacity of the expansion tank ..... building pressure all the way to the PRV increasing the preesure inside the home.

    Just a thought.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  2. #22
    Join Date
    Aug 2007
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    1,131

    Default Re: New Expansion Tank/T&P Valve Still Leaking

    Yeah, ........but.....(there's always a "yeah,but"...right?)


    In theory, an out-of-control heating element could definitely be the cause, but....is everyone in the household asleep at the wheel as regards that temp thingie?

    I would like to think that if that was happening (the cause)...that someone would have noticed the scalding hot water comin' outta the faucets by now.

    And so....I'm gonna ask what the unregulated pressure is on the city supply line. 140 psi, maybe? This *could* be a PRV problem yet.

    Edit: One way I can see the out-of-contol thermo/element being the problem and not being noticed is *if* the WH is also plumbed in backwards. This would mix the incoming cold with the outgoing hot. My neighbor did that and LEFT IT that way for 25 freakin' years ...even after I pointed it out to him! Said it was "too much trouble to mess with". Aye, carumba. Instead, they turned the thermo up as high as possible and went to watch TV. LOL Put a new WH in there for them this last winter while they were gone to AZ. Ain't hooked up backwards no more. LP consumption has gone way down. Imagine that. <G>

    (Or *maybe* (big maybe) an out-of-control thermo would go unnoticed *if* there is a major cross connection somewhere in house plumbing. Like maybe... one of them thar Y-thingie mixers on a faucet set with both lines open to it. But this would make for some very warm "cold" water and someone shoulda/woulda noticed that by now, too.)

    (Or maybe one of those Moen single-handle bath/shower cartridges that are reknown for cross-connecting when parts wear out inside.)
    Last edited by goldhiller; 09-17-2008 at 10:56 AM.

  3. #23
    Join Date
    Sep 2008
    Posts
    32

    Default Re: New Expansion Tank/T&P Valve Still Leaking

    We haven't noticed any scalding hot water. I'll check the temp with a thermometer tomorrow. Is there a way the heater is staying on and increasing the pressure, but not the water temperature?

    I don't think there are any crossed lines. Hot is hot and cold is cold in every faucet.

    I know the WH isn't plumbed backwards.

    I'll have to check and see what the incoming city pressure is. I assume the water dept. will have to check for me. I'm a firefighter by trade, so I could borrow a hydrant pressure gauge from work and check the pressure in the hydrant line, although this won't necessarily tell me the incoming pressure into the house (or will it?). There could be a PRV between the primary distribution line and my house supply, right?

  4. #24
    Join Date
    Aug 2007
    Posts
    1,131

    Default Re: New Expansion Tank/T&P Valve Still Leaking

    Heck...the city water department should know what the pressure is. *Should*, anyway. A simple phone call should answer the question.

    You might also check to see if your PRV has a backflow device. If it does and it's not functioning properly, this could be the cause...or a contributing cause. Yeah, the expansion tank *should* negate the need for that backflow relief, but.... something or *things" is causing this problem and nothing should be taken for granted or overlooked now.

    BTW, I'm curious as to how you're determining that the ET is taking on water and then leaving it out. How is it connected to the plumbing line and where does it reside? (Physically speaking. Already know it's hooked up to the cold side of things) Couple pics maybe?
    Last edited by goldhiller; 09-17-2008 at 11:37 AM.

  5. #25
    Join Date
    Sep 2008
    Posts
    32

    Default Re: New Expansion Tank/T&P Valve Still Leaking

    I'll give them a call.

    The tank is connected via a braided hose to a tee fitting on the colds side. The tank sits atop the cabinet in the bathroom. I can pick it up to see whether it is full or not.

    I'll take a peek at the PRV tomorrow and see if I can determine anything.

  6. #26
    Join Date
    Jun 2007
    Location
    West Jordan, Utah
    Posts
    84

    Default Re: New Expansion Tank/T&P Valve Still Leaking

    Do you have any other appliances or connections to your water lines that may be causing the excess pressure? Maybe the water heater isn't the problem, it is just the point where the pressure is relieved.

  7. #27
    Join Date
    Aug 2007
    Posts
    1,131

    Default Re: New Expansion Tank/T&P Valve Still Leaking

    Quote Originally Posted by mpriley05 View Post
    I'll give them a call.

    The tank is connected via a braided hose to a tee fitting on the colds side. The tank sits atop the cabinet in the bathroom. I can pick it up to see whether it is full or not.

    I'll take a peek at the PRV tomorrow and see if I can determine anything.
    That is kinda what I suspected. Haven't seen one yet with a clear housing.

  8. #28
    Join Date
    Aug 2007
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    1,131

    Default Re: New Expansion Tank/T&P Valve Still Leaking

    Quote Originally Posted by Blake View Post
    Do you have any other appliances or connections to your water lines that may be causing the excess pressure? Maybe the water heater isn't the problem, it is just the point where the pressure is relieved.
    Interesting notion.

  9. #29
    Join Date
    Sep 2008
    Posts
    32

    Default Re: New Expansion Tank/T&P Valve Still Leaking

    Do you have any other appliances or connections to your water lines that may be causing the excess pressure? Maybe the water heater isn't the problem, it is just the point where the pressure is relieved.
    Nope. There are no other heat or pressure producing appliances hooked up to the water line.

    It sounds like the options here are to either:

    1. Get a new water heater to eliminate the possibility of a broken thermostat or heating coil that won't shut off (and make sure there are no heat traps or check valves in the new heater)

    or

    2. Get a new PVR that permits backflow into the city system (assuming the city system is less than 140 PSI)

  10. #30
    Join Date
    Jun 2007
    Location
    West Jordan, Utah
    Posts
    84

    Default Re: New Expansion Tank/T&P Valve Still Leaking

    The city may have a backflow preventer at the meter setter, if this is the case a new PRV will not change any thing.

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