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Thread: replacement pump sizing

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    replacement pump sizing

    I have a question on replacement pump sizing. My 16 year old Aquatools 1HP pump died in September so I need to replace it this Spring.

    I could not find an aquatools replacement but I assume I can use another brand. I saw a few 1 HP pumps
    http://www.amazon.com/Hayward-SP1580...ct_top?ie=UTF8

    and

    http://www.amazon.com/Blue-Wave-NE61...B00B4ZNKO8#Ask

    Both are 1HP. My filter is an Aquatools AT3115 which states a filtration rate of 20GPM. The pool is small (18' round/ 7800 gallons)

    I read the GPM of these pumps are 38 or 43 GPM. I think it said something that reduces based on the size or the hoses, distance, etc. the pump is located close to the pool.

    Are these replacement too strong for the size of my sized filter and could possibly damage it?

    here are a few photos I took to see scale of filter, etc.






    Thanks!
    Steve

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    Smykowski's Avatar
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    Re: replacement pump sizing

    I am terrible at pump sizing, but hopefully this bump will get you a little visibility and help from those that can.
    33' round, 23,000 gal AG vinyl , 1HP 2spd PowerFlo Matrix downsized with 3/4HP impeller (X2), Hayward S180T 150# sand filter (X2), Hayward H250 NG heater Pool Store year 1 - $850 for 2 months; Pool Store year 2 - $440 for 2 months, TFPC year 1 - $170 for 4 months; TFPC year 2 - $95 for 4.5 months
    The most important article on this site - The ABCs of Pool Water Chemistry

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    Re: replacement pump sizing

    The filter would be too small for even a 3/4 hp pump. It's not so much that the pump can damage the filter (although very rarely it can) it's more that the pump aggressively forces the water through the filter and results in decreased filtration.....possibly even returning debris to the pool (but not likely)

    So I would get a bigger filter....perhaps 40-50 gpm. A used filter is not a bad bet so check craigslist.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: replacement pump sizing

    Thanks for the replies Smykowski and duraleigh.

    duraleigh- OK, I'll check craigslist if there are any filters a bit larger. I rarely have issues with the water as it's clean. It is common for a manufacturer to put a pump too large for the filter? I didn't but this...the previous home owner did.

    I am also wondering if instead of replacing the pump, I would be better off trying to find a direct replacement for the AO Smith motor and keep the same pump. It is in pretty good shape. I know the current pump works with this filter.

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    Smykowski's Avatar
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    Re: replacement pump sizing

    Quote Originally Posted by stevesul View Post
    Thanks for the replies Smykowski and duraleigh.

    duraleigh- OK, I'll check craigslist if there are any filters a bit larger. I rarely have issues with the water as it's clean. It is common for a manufacturer to put a pump too large for the filter? I didn't but this...the previous home owner did.

    I am also wondering if instead of replacing the pump, I would be better off trying to find a direct replacement for the AO Smith motor and keep the same pump. It is in pretty good shape. I know the current pump works with this filter.
    Yes. There seems to be this idea that the bigger the pump the better the system. Probably because there is a misplaced emphasis on "turnover."

    If the pump is fine, replacing the motor only is a fantastic idea. If you can find a 2 speed, you'll be doing even better. The best would be to buy a 3/4hp 2-speed motor only. Just be aware that if you downsize the motor, you'll have to buy a smaller impeller for it as well.
    33' round, 23,000 gal AG vinyl , 1HP 2spd PowerFlo Matrix downsized with 3/4HP impeller (X2), Hayward S180T 150# sand filter (X2), Hayward H250 NG heater Pool Store year 1 - $850 for 2 months; Pool Store year 2 - $440 for 2 months, TFPC year 1 - $170 for 4 months; TFPC year 2 - $95 for 4.5 months
    The most important article on this site - The ABCs of Pool Water Chemistry

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    Re: replacement pump sizing

    Quote Originally Posted by Smykowski View Post
    Yes. There seems to be this idea that the bigger the pump the better the system. Probably because there is a misplaced emphasis on "turnover."

    If the pump is fine, replacing the motor only is a fantastic idea. If you can find a 2 speed, you'll be doing even better. The best would be to buy a 3/4hp 2-speed motor only. Just be aware that if you downsize the motor, you'll have to buy a smaller impeller for it as well.
    Bigger is Better is the american way. lol. Thanks for the info...it looks like I have a few different ways to go with this (larger filter, smaller pump, or replace motor).

    One more question...are the hose sizes pretty much standard if I did get a new pump? In the photo above...I have a wide clear hose that runs from the pump to the filter and then two narrower hoses that run from and to the pool. Thanks!

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    Smykowski's Avatar
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    Re: replacement pump sizing

    If you replace just the motor, nothing about your setup would change, so you could reuse all of the hoses.

    I don't know much about flex pvc, but I'm pretty sure it's standard and you can buy what you need from a hardware store.
    33' round, 23,000 gal AG vinyl , 1HP 2spd PowerFlo Matrix downsized with 3/4HP impeller (X2), Hayward S180T 150# sand filter (X2), Hayward H250 NG heater Pool Store year 1 - $850 for 2 months; Pool Store year 2 - $440 for 2 months, TFPC year 1 - $170 for 4 months; TFPC year 2 - $95 for 4.5 months
    The most important article on this site - The ABCs of Pool Water Chemistry

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    Re: replacement pump sizing

    OK thanks again!

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    Re: replacement pump sizing

    I just wanted to close the loop on this. I purchased a 3/4 HP pump and it was a quick swap with all the existing hoses, etc fitting great. My winter cover teared this year and the pool had a lot of leaves, etc. in it when I opened it. The new pump works great with the existing sand filter and the pool was crystal clear in a few days. The other benefit was how quiet the new pump is.

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