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Thread: Pump/Filter Sizing

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    Pump/Filter Sizing

    I'm about to get a 21' round ABG and want to know what would be the best size pump/filter(sand) for this pool? All the pool stores around here sell that pool with a 200# sand filter and 1.5hp pump. I'm pretty sure the pump is too large and maybe the filter too small, but could use some suggestions. The pump/filter will be right next to the pool so the pump won't be pushing far at all. Also, would a 2 speed be better than a single speed? I plan on running the pump on a timer, instead of all day. I'm thinking of using the Liquidator. I doubt this would make a difference, but I don't know.

    I don't know if 2 returns are better than one, but if I do decide to get 2 and use one with a fountain, will this affect the size of the pump I buy?

    Thanks
    21' Round AGP, 10k gallons - 2hp 2spd pump - 300lb sand filter - Stenner Chlorine Injector - Pool Rover

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    JasonLion's Avatar
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    The usual rule of thumb is that the standard package gives you too large of a pump and too small of a filter. A 1 1/2 HP motor is probably too large for that pool (depending on the SF), but a 200# sand filter is alright, though you could easily go larger. A large pump wastes electricity. You could probably switch to a 3/4 HP full rated or 1 HP up/max rated pump and still be fine. A two speed pump would be even better. Low speed is a very efficient way to filter and high speed is available when you want to vacuum.

    One issue to watch out for is that there are several different ways of rating pumps, so a 1 HP full rated pump might actually be the same as a 1 1/2 HP up rated pump. To really compare pumps you need to know the service factor (SF). The brake HP, the HP available to move water around, is equal to the listed HP times SF.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    I have a 3/4hp Waterway, so I will check the numbers you talked about. Hopefully these are written on the pump? With the 2 speed, it is better to run 24/7 on low, right? Will this affect the Liquidator, since it dispenses while the pump is running? Hopefully, I can just use the pump I have and upgrade my sand filter (only 100lbs).

    Thanks
    21' Round AGP, 10k gallons - 2hp 2spd pump - 300lb sand filter - Stenner Chlorine Injector - Pool Rover

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    1 and 1/2 hp pump is on my HUGE POOL. so i think your pump is way to big and will waste electricity and probably not filter efficently since it will be pushing the water through so quickly.

    a 2 speed pump would be your best bet.

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    What about the 2 speed? Is it best to run it 24/7 or set it on a timer?

    Thanks
    21' Round AGP, 10k gallons - 2hp 2spd pump - 300lb sand filter - Stenner Chlorine Injector - Pool Rover

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    JasonLion's Avatar
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    How long you want to run the pump varies depending on the relative size of the pump and the pool, how warm the water is, and how many people are using the pool. Even though a two speed pump on low speed might often need run times around 24 hours a day it is better to have a timer. In the spring and fall, when the water is cooler, you won't want to run the pump for as long as you will in mid summer.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Sounds good. Thanks everyone for the help.
    21' Round AGP, 10k gallons - 2hp 2spd pump - 300lb sand filter - Stenner Chlorine Injector - Pool Rover

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    I just checked the numbers on my waterway pump. 3/4hp. and service factor= 1. What does this mean?
    21' Round AGP, 10k gallons - 2hp 2spd pump - 300lb sand filter - Stenner Chlorine Injector - Pool Rover

  9. Back To Top    #9
    Quote Originally Posted by kmb997
    I have a 3/4hp Waterway, so I will check the numbers you talked about. Hopefully these are written on the pump? With the 2 speed, it is better to run 24/7 on low, right? Will this affect the Liquidator, since it dispenses while the pump is running? Hopefully, I can just use the pump I have and upgrade my sand filter (only 100lbs).

    Thanks
    How long you run your pump depends how many gals your pool is and how many gals your pump pushes. In my case I run my 2sp pump on low 10hrs a day. I get one full turn over (filtering the volume of my pool in 24 hrs) at 40 gals per min on low I filter 24,000 gals of water every 10 hrs. On high, I would probably filter the pool in 5hrs but at a higher cost of electricity. I only use high when using my water features or vacumming in a hurry.

    I have a Liquidator and keep the flow meter at 1 ( one of the lowest settings) and I keep my CL at 4-5ppm with that setting. I did have to remove the check valves ( plastic device that allows water to flow one way) because you need a lot of suction to open the valve. SInce I use my pump on low, there was very little suction to open the valve. As long as the Liquidator is above the pool water level, you can remove the check valves as I did. If you are pushing more than 40 gals per minute it probably does not make a difference if you have the check valve installed.
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    kmb,

    I just checked the numbers on my waterway pump. 3/4hp. and service factor= 1. What does this mean?
    As Jason said above:
    One issue to watch out for is that there are several different ways of rating pumps, so a 1 HP full rated pump might actually be the same as a 1 1/2 HP up rated pump. To really compare pumps you need to know the service factor (SF). The brake HP, the HP available to move water around, is equal to the listed HP times SF.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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  11. Back To Top    #11
    JasonLion's Avatar
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    Your pump has a brake HP of 3/4 HP. For comparison, the WhisperFlo full rated 3/4 HP pump has a brake HP of 1 1/4 HP. I would expect that pump to be fine for a fairly small pool.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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