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Thread: Correct size for Thermostatic valve and controls

  1. #1

    Default Correct size for Thermostatic valve and controls

    Can anyone tell me if a 3/4 thermostatic valve is the correct choice (vs the 1/2 model) when used with both a shower head and a hand held shower unit? Each shower head will be controlled by volume control. Not sure about whether to use 1/2 or 3/4 inch for the volume controls. The hot and cold water feeds are 1/2 inch. My water pressure is 50 PSI with a flow rate of 7 GPM. If I was to use the 3/4 inch parts should the piping be 3/4 inch or reduced to 1/2 between the thermostatic valve and the volume controls and the volume controls to the shower heads?
    I contacted the Manufacturer, Grohe, and all they said was that with 2 outlets I could use either. They were not much help.
    Steve Odian

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    By federal regs, a showerhead can't use more than 2.5gpm, so with two heads max, it probably won't make much difference...I concur. It gets to be more of a factor if you've got more heads. The 1/2" valve is less expensive. Now, if you had 3/4" supply lines and were filling a big tub, that would be a different story.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3



    Thankyou for the response


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