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T&P question

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  • T&P question

    I was at another site looking at picture of a pressure only valve above a water heater and can't for the life of me remember what it was for.

    The only thing I can think of was (if it had a lower pressure rating) it would pop off (and drain to the outside) before the tp on the tank. This would be if in a basement without a drain or access to the outside. That would still leave the Temp. to drain into the basement though.

    I remember learning about this a long time ago but It must not have stuck.
    Brent

  • #2
    Re: T&P question

    The pressure only valve is required to be on the cold water system if you have a closed water system. A closed water system is a water system with a prv installed on it, a prv is a pressure reducing valve. prv's prevent the water in a system from returning to the city main if a high pressure event accures. A city meter will spin backwards if this event accures. as I am sure you are aware a prv reduces the incoming water pressure from the city.
    sigpic

    Robert

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    • #3
      Re: T&P question

      as long as there is no check valve or backflow preventer. the thermal expansion will go back through most modern pressure regulators. keep in mind that the city main has to be lower than the relief valve setting for this to happen.

      pre 1997, a combination temp/ press, relief valve was not required in the city of la, as long as you had a cold water relief valve and no hot water check valve.

      now no watts 210 valve. what are we going to do?

      rick.
      phoebe it is

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      • #4
        Re: T&P question

        Robert,

        You should only be using PRVs which have a bypass.

        Mark
        "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

        I never lost a cent on the jobs I didn't get!

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        • #5
          Re: T&P question

          most of the meters I come in contac with have a built in check at the saddle

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          • #6
            Re: T&P question

            I have seen pressure only relief valves on submersible well systems.
            Push sticks/blocks Save Fingers
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            • #7
              Re: T&P question

              Out here we have to install a thermal expansion tank in the cold water line no relief valve required except for the t&p on the heater.
              sigpic

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