Bathtub water flow rate question

Discussion in 'Shower & Bathtub Forum & Blog' started by texcollins, Mar 22, 2008.

  1. texcollins

    texcollins New Member

    Messages:
    1
    Location:
    Texas
    I need to put a faucet valve in my bathtub and have been presented with two choices, either a 14.9 GPM@45 PSI or a 7.2 GPM@45 PSI. Can anyone tell me what a standard bathtub flow rate is? There is about $150 difference between the two choices and I'm wondering the flow rate in a typical bathtub is so I might have an idea how to compare. Thanks!:confused:
  2. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    One question would be what size pipe you have feeding the tub, and at what length from the main/water heater. 1/2 inch pipe will not deliver 14 GPM, without way too much pressure drop. You would have a water velocity of 14 feet per minute ( way too much ) and a pressure drop of 22 psi in 40 feet.
    Last edited: Mar 22, 2008
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,143
    Location:
    New England
    As noted, the biggest thing is what size are your supply lines? My guess is that the higher flow rated one expects 3/4" supply lines, and you won't get that flow unless they are that big.
  4. Redwood

    Redwood Master Plumber

    Messages:
    7,450
    Location:
    Connecticut
    The larger flow tub fillers are primarily for large tubs. Yes the supply would have to be there.
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