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Thread: Water Heater Pressure Relief Valve Leaked About a 2 Quarts of Water

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    DIY Junior Member hudson's Avatar
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    Default Water Heater Pressure Relief Valve Leaked About a 2 Quarts of Water

    My water heater and pressure relieve valve were installed by me in 2000. The tag on the pressure relieve valve says 150 PSI. I'm on a city water system. I don't have any backflow valves or pressure tanks in my system. I test the valve at least once per year. I have a quart jar under the pipe leading from the pressure relief valve. About 2 quarts of very hot water came through the side mounted valve. I operated the valve 5 or 6 times; it has not leaked a drop since then...that has been two hours. The water is definitely coming through the valve and not from around the sides of the valve. I read a number of other threads. We've been using hot water on and off all day for bathing, and washing clothes/dishes. What's my next move?

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    Master Plumber Redwood's Avatar
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    What is your water pressure?

    Do you have a pressure reducing valve installed?


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    In the Trades Gary Swart's Avatar
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    The point of Redwood's question is, do you have a pressure regulator valve like the one pictured? If you do, then you should have a thermal expansion tank between the pressure regulator and the water heater. Otherwise, when the water heats, it expands. The pressure regulator prevents the expansion from being absorbed by the city water main so when the pressure reaches the limits of the T/P valve on the tank, it releases the excess pressure. Now, I can not tell you when this has just now begun to happen, usually it is an immediate condition. It is possible the T/P is failing although that is unusual if it's only a couple of years old.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Or, if you have an expansion tank, it has failed.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member hudson's Avatar
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    "What is your water pressure? Do you have a pressure reducing valve installed?" Expansion tank? Age of valve?

    I don't know my water pressure...but I'm willing to get it checked. I think that I read on other threads to buy a device for about $10 and put it on an outside spigot.

    No pressure reducing valve.
    No expansion tank

    Not one drop of water has leaked since I first found the big puddle in the garage. At that time, I worked the valve on the water heater several times.

    The pressure relief valve on the side of the water heater is a year 2000 model...that's 9 years old.

    I called my local utility to find the water pressure...no answer...holiday?
    I'm on my way to get a pressure gauge...I'll check the pressure and post the result.

    Thanks for your assistance!
    Last edited by hudson; 07-03-2009 at 06:50 AM.

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    DIY Senior Member SteveW's Avatar
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    Here's another test that would help make the diagnosis. Hook up your new pressure gauge to a hose bib (for example, your cold water source for your washing machine) and see what the pressure is. Then, run some hot water by turning on a tub faucet to full hot and let it run for 5-10 minutes. Then shut it off, make sure no one in the house runs any water and watch the gauge.

    If you have thermal expansion going on, your pressure will rise during this period - possibly dramatically.

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    DIY Junior Member hudson's Avatar
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    The water pressure was 25 psi.

    When I went to hook up the pressure tester, I had to remove a garden hose. The spigot was on, a valve at the other end of the hose was closed. The hose was in the sun. The temperature was over 90 degrees yesterday. The hose in the back yard was the the same...spigot on...valve at the other end of the hose closed. Two garden hoses...both in the summer sun...both spigots on...would that increase pressure in the system?

    again...no leaks or problems since yesterday.
    Last edited by hudson; 07-03-2009 at 08:15 AM.

  8. #8
    DIY Senior Member SteveW's Avatar
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    25 PSI is pretty low.

    I doubt that the thermal expansion you would get from hoses in the sun would be enough to cause house PSI to exceed 150 PSI. Also, the hose would burst before that.

    I'd still opt to take 10 minutes and do the test I mentioned.

  9. #9

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    Quote Originally Posted by hudson View Post
    The water pressure was 25 psi.

    When I went to hook up the pressure tester, I had to remove a garden hose. The spigot was on, a valve at the other end of the hose was closed. The hose was in the sun. The temperature was over 90 degrees yesterday. The hose in the back yard was the the same...spigot on...valve at the other end of the hose closed. Two garden hoses...both in the summer sun...both spigots on...would that increase pressure in the system?

    again...no leaks or problems since yesterday.


    My temperature / pressure relief valve went bad after about a year of use. The temperature part of the valve went bad. I changed it and all is well. They only cost around $15, so buy a new one and change it out.

    My normal water pressure is around the 60 PSI area.
    Samuel James Witwicky

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