Flow test from 2 shower heads - is 3 GPM sufficient?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by murphy290, Dec 2, 2013.

  1. murphy290

    murphy290 New Member

    Messages:
    7
    Location:
    new york
    Our new shower will have a fixed shower head and a handheld, with a thermostatic valve and separate volume controls so that the shower heads can be used separately or at the same time. Both shower heads are rated at 2.5 gpm. We did ten-second flow tests and got 4 gpm at each outlet when turned on separately, and 3 gpm when they were both on at the same time.

    Are these results normal? Since we have more than 2.5 gpm, should we have enough volume/flow as time goes on?

    Thanks
  2. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

    Messages:
    4,549
    Location:
    North Vancouver, BC
    Why not double check your math.

    A larger bucket (like a garbage can) will give you a more accurate reading.

    Perhaps the flow restrictors are removed from the fixtures? 4 GPM is not a lot if your worried about flow rates down the drain and 4GPM is a lot if you are wanting lots of water. I would not freak out over these numbers.

    When flow rates get over 12-14 GPM you need to make sure the drain can handle it. Over 16-18 GPM and head water build up over the drains grate can measure as high as 1/2" in my private testing.
  3. murphy290

    murphy290 New Member

    Messages:
    7
    Location:
    new york
    I should have explained - I didn't have the actual shower heads on the outlets, just a goose neck. (One shower head is still on order.) I'm more concerned that I won't have enough flow, so I wanted to check before we go any further in the remodel. Is 4 gpm for each when on separately and 3 gpm with both on normal?

    I can install one of the shower heads plus use an old one to do another test if that makes sense. What do you think?

    Thanks
  4. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

    Messages:
    4,549
    Location:
    North Vancouver, BC
    I would do that.

    To much water flow and you will need a larger hot water tank!
  5. murphy290

    murphy290 New Member

    Messages:
    7
    Location:
    new york
    Yes - either a larger hot water tank, or we'll have to take very quick showers!

    Thanks again.
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