Gas Hot Water Heater Tank and Pressure Relief Valve

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by skadoo323, Jan 12, 2009.

  1. skadoo323

    skadoo323 New Member

    Jan 12, 2009
    Hello Everyone,

    I have a gas water heater tank in my house, which does in fact have a Pressure Relief Valve from the side like most hot water heater tanks. Recently I have been noticing some water in the drip pan below the water heater. The water collects in the pan only when the water tank heater is on and heating the water. Above the hot water heater tank are two pipes, one for cold water which I think goes into the hot water heater tank and then another pipe which carries the hot water from the hot water heater tank (not sure if it matters, but these pipes are copper). On the cold water pipe which goes to the water heater tank, I noticed that there is a pressure vale of some sort. Unlike the main water line's pressure regulating valve, this one is not adjustable. Also this valve, which is somewhat in the shape of a "T" has an output line which is I think 1/2" PVC. I looked at my parent's place and my sister's place, but neither of their water tanks have a pressure regulating valve such as this which is connected to the cold water pipeline going into the hot water heater tank.

    The water collected in the pan comes from this PVC piping, which is from the pressure regulating valve that is connected to the pipe providing cold water to the hot water heater tank. I noticed when the water is dripping from this PVC pipe, the copper cold water line pipe going to the hot water heater feels warm.

    Any ideas on why the dripping occurs? Is this valve on the cold water line going to the hot water heater even needed? Just asking because a maintenance employee at one of my employer's offices said it is not needed and I could just plug it. I wanted to get some additional input before doing anything. Thanks!
  2. Gary Swart

    Gary Swart In the Trades

    Sep 1, 2004
    Yakima WA
    I have no idea what that extra valve you describe is or is for, but I can tell you why your T/P valve on the water heater is leaking. You need a thermal expansion tank in the cold water line. The pressure regulator valve on the supply line has a check valve built into it. When the water heater heats, this causes the water in the tank to expand. In homes with no pressure regulator, this expansion is absorbed by the city water main. but in your case, the PRV stops this from happening. This build pressure in you water heater to the point that it trips the T/P valve. A thermal expansion tank absorbs this expansion. Perhaps one of the professional plumbers can identify that other "valve" or whatever it is, but I tend to think it can be eliminated.
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  4. kingsotall

    kingsotall Plunger/TurdPuncher

    Aug 17, 2008
    Hand copper part cleaned ready to go
    Flagstaff, AZ Sitting on an upside down 5 gallon b
    Check out this thread:
    Pics included

    And if this is similar to your pipe in question keep in mind this response:

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