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Thread: Variable flow volume control with a 2.5 GPM head

  1. #1
    DIY Junior Member let it flow's Avatar
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    Default Variable flow volume control with a 2.5 GPM head

    Will I need a variable flow volume control for my new 2.5 GPM shower head? Or will it work OK to just use the on/off feature of a pressure balanced temperature mixer?

    This will be going into a remodel with new piping. Right now I have a seperate hot and cold valves that mix at the divertor and then goes to a showerhead that could sink Noah's ark. But I am sure the permit inspector will make me install a 2.5 (or lower!) GPM head, as well as replace the valve with a temperature contolled one. It seems that the low flow head will need all the pressure it can get, in order to spray right, with enough "blast" pressure and water volume to rinse the soap off. I suspect that a volume control valve would be turned wide open most of the time. I also suspect that a useful volume control would need to have a pressure/flow characteristic that closely matches that of the head, in order to get a flow that changes evenly over the full rotation range of the valve.

    Give me your thoughts and experiences of using just an on/off control. Is the spray sometimes too much like "stabbing needle" jets?
    How do I go about choosing a valve with the appropriate pressure/flow curve? Valve spec sheets don't even touch that issue.

  2. #2
    Moderator & Master Plumber hj's Avatar
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    A SINGLE shower head does NOT need a volume control and ANY installation which uses "positive" shutoff volume controls also needs a control unit with integral check valves. However, a valve with a single handle usually only controls the temperature, the volume is at full flow as soon as it is turned on. A Delta 1700, for example, has one "set it and forget it" temperature lever and a coaxial second on/off volume control handle.

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
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    Code requires antiscald...it does not dictate how that is achieved. that can be either pressure balance or thermostatic. A thermostatic may have a pressure balance in it as well, depending on its response rate to changes in temp and pressure.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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