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Pressure relief valve

Coqui98 | Posted in Energy, Heating & Insulation on January 5, 2010 09:06am

Last month I lowered the temperature on my water heater to save on my gas bill. Unfortunately the pressure relief valve then started to release about one cup of water daily. I replaced the valve but the leaking continued. Some breaktime bloggers recommended that I raise the temperature back up in increments to see if the leaking would stop. The temperature is now back where it was originally (above “HOT”) and the leaking continues. I have an expansion tank and do not see any leaks and this all started when I originally lowered the temperature. Does anyone have any idea what is causing the leaking and/or can suggest what to try next? Thanks, Carlos

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  1. danski0224 | Jan 05, 2010 09:24am | #1

    Is the expansion tank waterlogged? Has it lost it's air charge?

    Have you tried opening the PRV in an attempt to dislodge any trapped crud on the valve seat?

  2. rdesigns | Jan 05, 2010 09:25am | #2

    If the water is not abnormally hot, like above 180 degrees, which apparently it's not, or you would have mentioned that, then I can think of three possibilities:

    1. Your relief valve is set to release at 125 pound pressure, and the the supply water is coming in higher than that at times. (A "spike" in pressure.) This would be for reasons beyond your control if you are on a municipal system, not your own private well. Check with neighbors to see if they have noticed a similar problem. This can happen even with a relief valve set to 150 pounds.

    2. It's possible that the expansion tank is water-logged, and not actually accepting any expanded water. This happens when the internal diaphram leaks and allows water to fill in where compressible air should have been.

    3. (Least likely) You got 2 bad relief valves in a row.

    1. Coqui98 | Jan 05, 2010 01:40pm | #3

      Thanks for the great comments. The valve checks out fine but how do I check the expansion tank to make sure it is also working?

      1. Shacko | Jan 05, 2010 02:00pm | #4

        You have to isolate the expansion tank from your

        system, if you have a valve to the tank close it and

        drain any water out of the tank, you then have to

        check your incomming water pressure and set the tank

        to that number (bicycle pump will work).

        If you have incomming pressure 80lbs or above you will

        need to install a PRV to get the pressure down first.

        1. rdesigns | Jan 05, 2010 03:43pm | #5

          Good advice.

          Also, I would assume that the exp. tank has a diaphram to separate the water and air compartments. If that diaphram is leaking, water will eventually refill the tank even after re-pressurizing with air.

          So, unless the OP wants to go thru this on a recurring basis, it will be good to replace the exp. tank fairly soon.

  3. danski0224 | Jan 05, 2010 07:45pm | #6

    Tap on the tank.

    The area on top near the water connection will have a dull thud.

    The area at the bottom by the air fitting will have a hollow sould.

  4. Coqui98 | Jan 06, 2010 03:19pm | #7

    Thanks again to all who have taken the time to offer cmments. Here is the update:

    -The exapnsion tank (Rudd Therm Guard) is mounted horizontally between the hot weater heater and the cold water valve.

    -When tapped on there are two different sounds, one on each half.

    -The side closest to the hot water tank is warmer than the opposite side.

    -I took off the plastic cover on the end and attached my electric air pump. The gauge read 60 lbs., some warm water came out and continued to leak until I put the plastic cover back on. The leaking has stopped but only because of the cover.

    I don't know if this is enough information but based on the above is the original problem caused by the expansion tank? If yes, can the tank be repaired or should just be replaced? If not, what is the next step?

    Any and all comments are welcome.

    1. Shacko | Jan 06, 2010 03:36pm | #8

      If you have water comming out of the air valve it's

      a good chance that the tank is bad. Most of the

      smaller tanks can't be repaired. Since you didn't

      give your incomming water pressure it's hard to say

      if the tank caused your problem.

      1. Coqui98 | Jan 06, 2010 04:16pm | #9

        Shacko,

        Thanks for the information. Just to confirm:

        -the side of the expansion tank connected to the water supply has water in it. The other half, seperated by the rubber diaphram should NOT have any water in it.

        -that side should contain only air and the recommended pressure should be around 12 lbs.

        Do I have it right?

        Carlos

        1. Shacko | Jan 06, 2010 05:20pm | #10

          You didn't read my previous
          You didn't read my previous post, the expansion tank

          has to be set to your INCOMMING pressure with the

          tank empty of water, 12 lbs. might pertain to a

          heating system but not to a water heater. The air valve

          should not have any water comming out of it. IF YOU

          ARE TALKING ABOUT A HEAT SYSTEM AND NOT A WATER HEATER

          DISREGUARD WHAT I'VE BEEN SAYING!

        2. DanH | Jan 06, 2010 05:35pm | #11

          The pressure on the air side should be measured with the water turned off and a valve open to relieve the (water) pressure. It should be a few pounds less than the static water pressure (when it's turned on).

    2. DanH | Jan 06, 2010 05:39pm | #12

      Note that it might happen that a SMALL amount of water would come out of the air side of the tank, due to water that, over the years, has transported itself through the diaphragm via osmosis. This should be, at most, a few ounces.

      1. Coqui98 | Jan 08, 2010 03:19pm | #13

        No, the water just keeps flowing if I take the plastic cap off.

        1. rdesigns | Jan 08, 2010 03:37pm | #14

          Sounds like you're getting
          Sounds like you're getting somewhere now.

          This means that the Exp. tank is waterlogged, which means it can no longer accept any expanded water from the WH.

          Likely,your water supply system is a "closed system", because water meters typically have a check valve on them, which is simply a one-way valve. So, any expanded water in your system now has no place to expand since the check valve prevents excess pressure from pushing back into the municipal system. Private well systems can act the same way because of the foot valve down in the well piping that is also a check valve.

          It appears that you just need to replace the exp. tank.

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