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Thread: Pump too big? Filter too small?

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    Pump too big? Filter too small?

    Hello all, first post but long time lurker. I have a few questions about my pool pump and filter. I've never really paid much attention too it until now. First, pool info.

    20 X 40 IG Vinyl, 33K gallons.

    Hayward Pro Filter S244T with multi-port valve
    Pentair SuperFlo Pump SF-N1-1-1/2 HP
    Motor label info:
    HP 1.5
    SF 1.1
    SFHP 1.65

    Two skimmers and main drain on suction side, two returns on pressure side. All 1.5 inch piping, no other features attached.

    The pool is at least 15 years old, probably older. It was already installed when we bought the house. New liner installed three years ago, new pump and filter installed by pool company four years ago after a tree fell on it. (that was fun)

    So...I was lurking as usual and happened across the sticky at the top of this forum, which got me to thinking (this could be good, could be bad ). After reading through it and doing some research, I think I may have an issue and would like to confirm.

    The filter pressure gauge reads 18 PSI on a clean filter, and after doing some measurements and "back of a napkin" calculations I am estimating the suction side head at 13. Reading the curve for this pump (and doing more math) it appears that I am pushing around 68GPM, which is above the filter rating on the label of 62GPM.

    Is this a problem or close enough?

    If I install a smaller motor (say 3/4 HP) I could bring the GPM down, but then I worry about turnover rate. I could get a larger filter (S270T), but that is a bit expensive.

    Any thoughts/opinions on this are welcome. I will provide more detailed information if needed. I would like to find a vacuum gauge and get a more accurate reading on the suction side, and I will update if I can make this happen.

    This isn't really an urgent issue, I'm thinking more long term so no rush. I want to carefully consider the options and find the best solution.

    Thanks!

    Tad

  2. Back To Top    #2
    Casey's Avatar
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    Re: Pump too big? Filter too small?

    Hi Tad,

    Others will tune in shortly and talk pumps all day long with you but the general rule is (since you have no bells and whistles on your pool) a 1HP 2 speed pump and getting the biggest filter you can afford.

    If you could fill out your signature with your pool specs, that would be great. What we need to know to answer your questions
    I'd bet you my bikini you'll never get TFP water from a pool store!

    24' Sharkline Venture De Filter

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    Re: Pump too big? Filter too small?

    By pushing more water through the filter than it is rated for, you end up wasting a significant amount of electricity and efficiency within your filter.

    A much better pump/filter match is a filter rated about 25% more than than the pump will produce.

    After all that, the math seldom works out so that it is immediately cost effective to rush out and buy new equipment.

    When you get to that point, Casey's suggestion of a 2-speed 1HP pump will be just about perfect and then a filter up around 90 gpm would be a nice fit with that energy saving pump.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    bobodaclown's Avatar
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    Re: Pump too big? Filter too small?

    If it working don't mess with it. When you have an issue, I'd swap out to a lower hp motor.
    17K Kidney Shaped Pool Concrete (Diamond Bright) Pool, 3/4 hp 2 speed 115V Sta-rite Duraglas PEA5D-180L/P2R5D-181L (Impeller C105-92PS Diffuser C1-216P), 1.5 piping, Pentair CC100 Filter , Heat Siphon 100K BTU Heat Pump Pool Heater, Flow meter Blue White Flowmeter Model No. F-30150P, Hayward Astrolight SP0581N, SWCG CalimarTitanium Edition TE45 , Dolphin Nautilus Plus with CleverClean, Lakeland Florida

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    Re: Pump too big? Filter too small?

    OK, got the signature fixed. Thanks for the initial responses.

    If it working don't mess with it. When you have an issue, I'd swap out to a lower hp motor.
    Ah, but that's the question! Technically its working, but what is it costing me to run it? If I'm overpowering the filter then how much more am I spending to maintain the pool, not to mention electricity costs? Its like using a helicopter to get to work when its five minutes away by car: Sure it gets me there, but driving a car is a much more effective solution.

    Would I save money over the life of a new pump or filter that works better vs. sticking with what I have? That is the question.
    33K gal vinyl IG, 1.5 HP SuperFlo pump, Hayward S244T sand filter (62GPM)

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    Re: Pump too big? Filter too small?

    I would start with the two speed pump and go from there. Your filter is more than adequate for low speed skimming, and it would be hard to get a return on your investment with a larger filter if you're only running on high a couple hours a week vacuuming.
    17,100 Gal 27' x 52" AGP steel wall vinyl; 44gpm Cooper sand filter; Hayward 1hp sp1580 single-speed; 1.5" plumbing, 1 skimmer/jet, inline chlorinator.
    Chlorine / CYA Chart | SLAM Process | Chlorine cost/fl. oz calculator

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    Re: Pump too big? Filter too small?

    That is the question.
    Do the math....starting with the electrical rate you are charged.

    As you develop your calulation, you will find there are a LOT of variables that only you can answer
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    mas985's Avatar
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    Re: Pump too big? Filter too small?

    Swapping out just the motor does not change flow rate. You need to change the impeller. In fact, you could just downsize the impeller and forget about changing the motor. If you want to get some additional benefit at some additional cost, then change the motor to a two speed. But it is really not worth downsizing a motor (and impeller) without going to a two speed.

    But assuming your head calcs were correct, your current pump would be using about 1800 watts. If you just changed the impeller, the power would drop to about 1400 watts. Add a two speed motor and running at low speed, the flow rate drops to half and the power drops to 323 watts.
    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 too big? Filter too small?

    +1 on what Mark said. If you go to a 2 speed motor on your existing pump and run on low speed, the reduced flow will work well with your filter. There will be significant energy savings that will pay for the motor in time. Doesn't sound like you are in a rush so consider choices and make the best one for you.
    17 x 35 fiberglass IG pool, 1.5 hp Pentair Superflo 2 speed pump, 150 ft2 Pentair Clean and Clear cartridge filter, Compupool SWG, Dirt Devil Electric Robotic Cleaner

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