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Thread: Pump Head / GPM and plumbing curve questions

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    Pump Head / GPM and plumbing curve questions

    hi guys, long time lurker, first time posting. Few questions on pump head and flow. i believe my pool is a bit over powered and want to swap impellers to slow the water flow, reduce the pressure/head overall and quiet the pump. when the motor gives up ill be looking into a VS but for now im tinkering with what i have.

    thank you for sharing the pool pump spreadsheet! really great asset!

    I have taken pressure readings right at the pump housing on the drain ports. Are these numbers enough to get an accurate GPM with out having to consider the specifics of the inline equipment and pipe runs/turns etc? i basically zeroed out the inputs on the psivac2gpm tab for pipe length/multiport etc.

    Pool mode:
    11 inhg- pump suction side
    28 psi- pump pressure side
    20 psi- filter gauge
    77ft head
    calculated plumbing curve 0.01067


    spa mode:
    14inhg- pump suction side
    31psi- pump pressure side
    25.5 psi- filter gauge
    87ft head
    calculated plumbing curve 0.04080

    if i swap the impellers to a smaller hp unit from the sp3215ee or even sp3210ee, will the total plumbing curve remain the same?

    is there anyway to calculate the % decrease in pressure/head/flow with these impellers?
    not sure how much pump i really need with the spa/heater combo.

    suction side is three separate intakes at 2inch each merging to one 2inch pipe in front of the pump. two skimmers and one floor drain
    return side is three separate pipes at 2inch each, one feeds 5, 3/4inch eyeballs into the pool the other feeds 6, 3/4 inch eyeballs into the spa, last one feeds water fountain coming out of the spa but valve is nearly closed 99% of the time.
    23,500 gallon IG gunite pool, 8.5 ft deep sloping to 3.5 feet deep.Spa with overflow into pool and fountain that comes out of center of spa
    Hayward Tristar sp3220EE main pump / Polaris pb4 booster with polaris 280 / Hayward DE620 filter and 740DE multivalve / Hayward H400FDN heater
    Hayward Aquarite with t15 salt cell

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    cfherrman's Avatar
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    Re: Pump Head / GPM and plumbing curve questions

    The head loss will change with a lower gpm. I think the best you could do is calculate your head loss at the lower gpm rate.
    Casey
    Intex 24' x 52" closed for winter 2018, 2 Main Drains, 1 Skimmer, 1 Return, PVC
    1/2 HP Intex Pump 633T w/ Taeglus TA-40 175 lb 19.5" Sand Filter, Auqabot Extreme Robot
    TF-50 and Taylor 2006 Test Kits, Quality Well Water, Fleck 5800SXT Water Softener

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    mas985's Avatar
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    Re: Pump Head / GPM and plumbing curve questions

    Welcome to the forum!

    Quote Originally Posted by Dean287 View Post
    if i swap the impellers to a smaller hp unit from the sp3215ee or even sp3210ee, will the total plumbing curve remain the same?
    Yes, plumbing curves will usually remain the same with flow rates. The only exception is when you have check valves in the system but the change is usually small.


    is there anyway to calculate the % decrease in pressure/head/flow with these impellers?
    Yes, you just need to determine the intersection of the new impeller head curve with the old plumbing curve. This will give you flow rates. You can then determine changes in pressure/suction with the change in flow rates using the pump affinity equations. The change in pressure ratio is proportional with the square of the ratio in flow rates. However, you need to take into account the elevation of the pressure measurement as this does not change with flow rate (i.e. static head). But if you are using the spreadsheet, it can take this into account. Just use the second column and the new equivalent pump. Everything else is taken care of, assuming you entered the correct elevation.


    not sure how much pump i really need with the spa/heater combo.
    If you have a spa, and this pump runs the spa jets, you should not change the impeller size or the spa jets will become much weaker. A better solution is to replace the current motor with a two speed motor so you can run the pump on low speed when using it for the pool and high speed for the spa.

    the other feeds 6, 3/4 inch eyeballs into the spa
    Are these just eyeballs or are they feeding spa jets?
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Pump Head / GPM and plumbing curve questions

    awesome thank you guys for the input.

    a variable or 2 speed motor is coming but hoping for another year or 2 from the current one.

    i did not realize there are actual spa jets. I have just eyeballs, not jets in the spa. visually they are identical to the pool returns. When i unscrew and remove the eyeball, the pipe is wide open just like the pool. There is an air blower that creates bubbles/extra force that is tee'd in after the pad

    so i guess i have a hot tub, not spa right?
    does this change your thoughts on needed flow when in spa/hot tub mode?
    23,500 gallon IG gunite pool, 8.5 ft deep sloping to 3.5 feet deep.Spa with overflow into pool and fountain that comes out of center of spa
    Hayward Tristar sp3220EE main pump / Polaris pb4 booster with polaris 280 / Hayward DE620 filter and 740DE multivalve / Hayward H400FDN heater
    Hayward Aquarite with t15 salt cell

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    mas985's Avatar
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    May 2007
    Location
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    Re: Pump Head / GPM and plumbing curve questions

    i did not realize there are actual spa jets. I have just eyeballs, not jets in the spa. visually they are identical to the pool returns. When i unscrew and remove the eyeball, the pipe is wide open just like the pool. There is an air blower that creates bubbles/extra force that is tee'd in after the pad

    so i guess i have a hot tub, not spa right?
    Actually, those are probably spa jets. The jets cannot be seen from the outside. The eyeball sits on the outside of the spa wall that you can see but the jets are deep within the spa wall. But the jet power is heavily dependent on the pump so the last thing you want to do is downsize the pump.

    Spa jets look something like this:

    1.jpg
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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