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Thread: Maximum GPM For 1.5" Pipe

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    ChuckDavis's Avatar
    Join Date
    Aug 2010
    Durham, NC

    Maximum GPM For 1.5" Pipe

    I just upgraded my Hayward SuperPump with a variable speed motor and 2.5 HP impeller. (See

    In Hayward's documentation for the SuperPump VS they recommend a maximum 45 GPM flow rate for 1.5" pipe.

    My new pump has a button to speed the pump up to maximum RPM for vacuuming, but at max speed it is putting out 65-70 GPM.

    Is the 45 GPM recommendation a "don't blow up your system" limit or am I safe to run at 65-70 GPM for vacuuming and backwashing? If 65-70 GPM is too high, is there a GPM flow rate between 45 and 65 that is safe?
    15,000 gallon IGP, epoxy surface, waterfall, borates (!), not closed in winter
    SuperPump with 2.4 THP EcoTech variable speed motor, Tagelus TA-60 filter with zeolite media, Liquidator, AquaComfort heat pump, Blue-White flowmeter, Smartpool Wall Climber
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    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: Maximum GPM For 1.5" Pipe

    You can run it as fast as you want. Not sure where they got 45 gpm but it there is no reason for it that I can think of.

    Pool pumps commonly push 60-80 gpm through 1.5" pipe.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Maximum GPM For 1.5" Pipe

    The particular filter wants 45-60 GPM when backwashing, and that range should also be just fine or even perhaps a little much when vacuuming.

    There is no specific flow limit, but as the flow rate gets higher the system gets less efficient. 45 GPM is a suggestion of the max flow rate for reasonable efficiency, but that is just an arbitrary suggestion.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Join Date
    Mar 2007
    San Rafael, CA USA

    Re: Maximum GPM For 1.5" Pipe

    See Maximum Flow Rates for PVC Pipes for more info. As Dave and Jason noted (posted around the time I was writing this), there really isn't a maximum, though it becomes very inefficient to use such narrow piping for higher flow rates since pump sizing and energy costs go up dramatically.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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