Bathtub water flow rate question

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

  1. texcollins

    texcollins New Member

    Mar 22, 2008
    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

    Aug 31, 2004
    San Diego, CA
    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
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  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    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.
  5. Redwood

    Redwood Master Plumber

    Dec 15, 2007
    Service Plumber
    The larger flow tub fillers are primarily for large tubs. Yes the supply would have to be there.
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