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Piping Shower Valves

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  • Piping Shower Valves

    Okay, you all were so helpful with my repiping the drain line - replacing a 1 1/2" CI pipe with a 2" CI No Hub to the original 2" bell hub connection - that I thought it wise to ask for your opinion on the water lines. So, here goes...

    The existing supply lines are 1/2".

    The thermostatic control shower valve has 3/4" ports.

    There are 2 volume control valves - one for a standard wall shower and one for a handheld shower. Each volume control valve has 3/4" ports.

    I was thinking of running 3/4" the feeds to the volume controls and the related showers from the thermostatic control instead of 1/2". The thinking behind this is to capitalize on the full 1/2" volume of each the hot and cold feeds.

    Is this going to somehow throw off the effectiveness of the thermostatic control valve? Create other problems? Never seen a plumber do this before but maybe it's because the materials cost more and they'd have to bring in 2 sizes of pipe instead of one. They're keeping it simple.

    Last edited by BarryP; 08-09-2013, 10:24 PM.

  • #2
    Re: Piping Shower Valves

    honestly the maximum flow by code is 2.5 gpm. of course a 1/2'' valve and piping will easily flow those numbers. the 3/4'' will probably flow in excess of 13gpm. post a link to the valve and volume controls plus the heads you're going to use.

    oversizing the hot can backfire if the heater is any real distance to the shower.

    now if you're running a carwash in the shower, with body wash heads and a rain head, then I would say 3/4'' is correct. or a large roman tub. but a standard head and hand held, 1/2'' should be enough as a typical 1/2'' valve will flow approx. 6 gpm. remember you also have heater concerns with too much flow and eventually a 2'' shower drain will also have a hard time keeping up with excess flow.


    now if you're running 3/4'' pex, then it's pretty comparable to 1/2'' id copper.
    Last edited by PLUMBER RICK; 08-09-2013, 10:04 PM.
    phoebe it is


    • #3
      Re: Piping Shower Valves

      Thank you for the quick response.

      There may be a possibility of swapping out the current showerhead for a rainhead. I know they use/ require lots of flow.

      Heater is hot water on demand.

      Yeah, it's probably overkill, but material costs for the pipe are $10 more (using 8' so 1 length) so I think I'm gonna test it out if there are no balance issues.

      Thanks again.



      • #4
        Re: Piping Shower Valves

        Yes if the ports are 3/4" betwen the valves and volume controls, then use 3/4". But I doubt you have 3/4" feeding the shower stall, valve. That was what I was refering to.

        What valve brand of thermostatic valve are you using. Grohe?

        phoebe it is


        • #5
          Re: Piping Shower Valves

          Last edited by BarryP; 08-10-2013, 11:56 AM. Reason: duplicate post


          • #6
            Re: Piping Shower Valves

            I got a great deal on ROHL, and that's the only brand my wife liked everything from sink to shower. All the same style and finish.

            The bathroom supply is 1/2". I'm not even thinking of changing that.

            Thank you for your help.