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Thread: Higher temperature water heater overflow valve?

  1. #1
    DIY Senior Member Melissa2007B's Avatar
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    Default Higher temperature water heater overflow valve?

    We're in the Denver burbs at about 5800 feet, which contributes to this. ( water boils at around 203 degrees here )

    This is the second time in 2 years I need to replace this valve and I'm tired of it. Why?

    We have a Aprilaire whole house humidifier that requires a 1/4" line of regulated temp 140 degree water from the top of the water heater. When it runs, it causes "stacking", where the trickle of hot water from the top causes a trickle of cold coming in the bottom, and the gas flame to come on to heat it, overheating the top.

    I just replaced this overflow valve, 2 years ago if I recall. I think they said it turns on at around 170 degrees?

    Right now it's dripping in the pan, and someone who was in the crawl space just told me there's a puddle down there now.

    We can't afford extravagant heroic solutions to this, like a circulating loop for the hot water, or all that. We're barely paying the bills here.
    ( This is a modular house and we'd love to do the loop thing, but there's insulation and plastic over the whole bottom down there. )

    So do they make valves like this that are a higher temperature? Like maybe 190 degrees?
    Melissa
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  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    A humidifier will work with using the cold water as the input. It might work better with warm water, but from the problems you're having, I'd just switch it to the cold side and forget about it. FWIW, my AprilAire unit has been using cold water as the feed for years, and works fine.

    There are higher trip T&P valves, but they wouldn't be a good idea at your altitude, even if it would fit (they're larger in diameter). They would also void the CSA certification, I think, and if you had problems with the tank, (it could blow up!) your insurance may not pay up, if you were still around to try to collect. http://media.wattswater.com/F-SF.pdf
    Jim DeBruycker
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  3. #3
    DIY Senior Member Melissa2007B's Avatar
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    I asked Aprilaire and they recommend only 140 degree regulated. Maybe it has to run much longer on cold. Remember, our cold is very cold here in winter.
    Melissa
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    Retired Defense Industry Engineer jadnashua's Avatar
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    My wintertime cold water can approach freezing, and yours can't be colder than that or it would freeze up. I've measured 33-degrees after a cold spell. Most T&P valves are rated to open at 210-degrees...because of your altitude, they may specify a lower-temp one. Keep in mind, the 'normal' 210-degree one would allow the water to flash to steam, should it ever be triggered for temperature and this is VERY unsafe.

    Running your WH at 140-degrees would also require a tempering valve per national code for the rest of the house.

    Are you sure that it isn't tripping because of pressure? If you have a closed water supply system and don't have an expansion tank, it could easily be opening because of pressure rather than temperature. Pick up a water pressure gauge with a second, tattle-tale hand, leave it connected to say the drain valve of the WH or your washing machine supply, and see what it says about pressure peak after 24-hours. It is very easy to get pressures to exceed the 150# of the T&P valve, and have it open because of that.
    Jim DeBruycker
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    DIY Senior Member Melissa2007B's Avatar
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    Not sure. Our outside hose water here has been known to go up to 90 or so PSI.
    Melissa
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  6. #6
    Retired Defense Industry Engineer jadnashua's Avatar
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    Code requires a PRV and an expansion tank when the supply water pressure exceeds 80psi...I'm thinking your problem may be more pressure than temperature. A PRV and an expansion tank may solve your problem, but first test the pressure. Remember, the T&P valve has TWO ways it can open.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  7. #7
    DIY Senior Member Melissa2007B's Avatar
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    OK. Like:
    http://www.freshwatersystems.com/p-1...indicator.aspx
    Wonder if Home Depot has em?

    I think the water was measured at the outside hose several years ago at 92 PSI. It may be pumped up to get uphill from Denver which is below us, to here, and then higher up.
    Last edited by Melissa2007B; 01-30-2013 at 10:13 PM.
    Melissa
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  8. #8
    Moderator & Master Plumber hj's Avatar
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    T&P valves open at 200 degrees, not 170, and therefore, NO ONE, makes "higher temperature" version, since that could create an unsafe condition in the water heater. Your diagnosis of the problem, and thus its cure, may be faulty.
    Licensed residential and commercial plumber

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    DIY Senior Member Melissa2007B's Avatar
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    Yeah OK. Now all I have to do is find a pressure gauge with adjustable red needle, locally, so we can figure this out SOON.

    Hmmm...

    http://www.homedepot.com/h_d1/N-5yc1...1#.UQqRCc_jFyI

    now if it's in stock...
    Last edited by Melissa2007B; 01-31-2013 at 07:43 AM.
    Melissa
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  10. #10
    Test, Don't Guess! cacher_chick's Avatar
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    I too have an Aprilaire humidifier tapped off the cold water supply. Been working fine for over 10 years.

  11. #11
    Jack of all trades DonL's Avatar
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    Quote Originally Posted by Melissa2007B View Post
    Yeah OK. Now all I have to do is find a pressure gauge with adjustable red needle, locally, so we can figure this out SOON.

    Hmmm...

    http://www.homedepot.com/h_d1/N-5yc1...1#.UQqRCc_jFyI

    now if it's in stock...

    They will most likely stock them.

    Do Your Cakes Rise High ?

    I hear the Brownies in Colorado are Far Out.
    Last edited by DonL; 01-31-2013 at 10:51 AM.
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  12. #12
    Retired Defense Industry Engineer jadnashua's Avatar
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    If your static pressure is over 80#, or it peaks higher, you need two things: a prv AND an expansion tank. Your existing plumbing may already be closed (i.e., a check valve from the water company, or maybe installed during construction), and without a working expansion tank (you might have one, but it has failed), the act of heating water WILL raise the pressure high enough to cause the T&P to release water unless some other weak point is bleeding off the pressure. The pipes are essentially rigid, and can't blow up like a balloon...something will give when the pressure rises. That's the purpose of the expansion tank. The two (prv + expansion tank) work together to keep the house pressure stable.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  13. #13
    DIY Senior Member Melissa2007B's Avatar
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    I just got the gauge from Home Depot and hooked it to the cold water line at the washing machine. It started out at 80 PSI about 40 minutes ago, and a check just now shows the red needle sitting at 92. But that red needle is very loose, a transient spike could kick it way up.

    The plumbing lady in Home Depot showed me some 3/4" and 1" regulators that she said can be put on the main line coming into the house, can withstand up to 300 PSI and only allow 50-70 PSI into the house.

    Update: Less than 2 hours and the red needle is up at about 98 PSI.
    Last edited by Melissa2007B; 01-31-2013 at 04:39 PM.
    Melissa
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  14. #14
    Test, Don't Guess! cacher_chick's Avatar
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    50 psi in a house is more than enough. I would speculate that most homes range from 30-50 psi.

  15. #15
    DIYer, not in the trades LLigetfa's Avatar
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    Put in a recirc pump and line. It will stop the stacking and give you hot water right away from a distant faucet.

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