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Thread: Optimal GPM flow rate for filtering and backwashing.

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    Optimal GPM flow rate for filtering and backwashing.

    I have a pentair TR-100 and a pentair Inteliflo VS (3hp) pump. I have installed a Flovis check valve / flow meter between the filter and heater. I think the pump is capable of 140 GPM. I'm sure this is the max under optimal conditions, but it will peg the flovis at 100 GPM pretty easy. I believe the max flow for my valve, filter, & heater is 125 GPM. My questions are, what is the max GPM I should ever run under any circumstance? What is the optimal GPM for the sand filter to work best? I understand slower is better for the filter. If I understand right more flow is slightly more efficient for heating than less flow. Is higher GPM better for backwash/rinse? If so, how much? I have 2" sch40 everywhere. Thanks for the help!
    Vinyl, 20' X 44' in-ground, 35,000 gallons, Inteliflo VS 3HP, Triton TR-100 w/ activate, MasterTemp 400,000K LP, Dolphin Supreme M500, Hydramatic Hydraulic Auto Cover, TF-100 Test Kit.

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    Re: Optimal GPM flow rate for filtering and backwashing.

    I run my VS pump at 1100 rpm for filtering, skimming and making chlorine with the SWG. And 1950 rpm for solar heating. It uses 150 ways and 550 watts respectively.
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    Re: Optimal GPM flow rate for filtering and backwashing.

    At 1100 rpm I think I'm only pushing 10 or 20 GPM. Is that enough for filtering?
    Vinyl, 20' X 44' in-ground, 35,000 gallons, Inteliflo VS 3HP, Triton TR-100 w/ activate, MasterTemp 400,000K LP, Dolphin Supreme M500, Hydramatic Hydraulic Auto Cover, TF-100 Test Kit.

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    Re: Optimal GPM flow rate for filtering and backwashing.

    Quote Originally Posted by crashxx View Post
    At 1100 rpm I think I'm only pushing 10 or 20 GPM. Is that enough for filtering?
    It is better than at max flow rate. At max flow rate, you can push the debris all the way through the filter. But in general, for a sand filter, it would be best to stay below 15 GPM/sq-ft if possible.
    Mark
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    Re: Optimal GPM flow rate for filtering and backwashing.

    A Pentair TR-100 is 4.9 sq.ft. filter The flow rate is 15-20 gpm/sq-ft, so between 75 and 100 gpm for backwashing would be fine. For filtering the slowest you can get away with is suggested

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    Re: Optimal GPM flow rate for filtering and backwashing.

    Ok, I think I'll set my max speed to 100 gpm. i will use that for back washing. I figure I'll run 80 gpm to heat, then set the other two speeds for filtering at 15 gpm and 40 gpm. Does that sound reasonable?
    Vinyl, 20' X 44' in-ground, 35,000 gallons, Inteliflo VS 3HP, Triton TR-100 w/ activate, MasterTemp 400,000K LP, Dolphin Supreme M500, Hydramatic Hydraulic Auto Cover, TF-100 Test Kit.

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    Re: Optimal GPM flow rate for filtering and backwashing.

    80 gpm to heat seems a bit high. What does the heater require?
    Mark
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    Re: Optimal GPM flow rate for filtering and backwashing.

    It doesn't have a requirement, just a max of 120 GPM.
    Vinyl, 20' X 44' in-ground, 35,000 gallons, Inteliflo VS 3HP, Triton TR-100 w/ activate, MasterTemp 400,000K LP, Dolphin Supreme M500, Hydramatic Hydraulic Auto Cover, TF-100 Test Kit.

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    Re: Optimal GPM flow rate for filtering and backwashing.

    According to this: http://www.pentairpool.com/pdfs/MasterTempAUOM.pdf

    Lower limit is 40 GPM so why not run at that instead?
    Mark
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    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: Optimal GPM flow rate for filtering and backwashing.

    I thought I had red it is slightly more efficient, at least on the heat/gas side, to run a higher GPM.
    Vinyl, 20' X 44' in-ground, 35,000 gallons, Inteliflo VS 3HP, Triton TR-100 w/ activate, MasterTemp 400,000K LP, Dolphin Supreme M500, Hydramatic Hydraulic Auto Cover, TF-100 Test Kit.

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    Re: Optimal GPM flow rate for filtering and backwashing.

    The heater is a little bit more efficient at higher flow rates while the pump is a lot more inefficient at higher flow rates. If you compare the two, the pump probably has the biggest financial impact.
    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: Optimal GPM flow rate for filtering and backwashing.

    I meant "read".

    - - - Updated - - -

    Got it. So would it be better to run at the minimum GPM or bump it up 10 - 15 GPM?
    Vinyl, 20' X 44' in-ground, 35,000 gallons, Inteliflo VS 3HP, Triton TR-100 w/ activate, MasterTemp 400,000K LP, Dolphin Supreme M500, Hydramatic Hydraulic Auto Cover, TF-100 Test Kit.

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    Re: Optimal GPM flow rate for filtering and backwashing.

    Why not compromise and run it at 60gpm to be safe

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    Re: Optimal GPM flow rate for filtering and backwashing.

    60 sounds good.
    Vinyl, 20' X 44' in-ground, 35,000 gallons, Inteliflo VS 3HP, Triton TR-100 w/ activate, MasterTemp 400,000K LP, Dolphin Supreme M500, Hydramatic Hydraulic Auto Cover, TF-100 Test Kit.

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    Re: Optimal GPM flow rate for filtering and backwashing.

    Heater manufactures generally put quite a bit of margin into their minimum numbers so I think it is very safe to run close to the minimum. Plus there are safeguards built into the heater such as pressure switch and thermal switch that will trip if the flow rate is too low.
    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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