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Thread: Must replace filter - getting differing size recommendations

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    Must replace filter - getting differing size recommendations

    So my 300lb sand filter split down the side. When questioning various pool companies about a replacement, I am getting a wide variety of sizes being recommended. I think I am going to switch to a cartridge filter due to having to use so much hose to properly backwash because of the design of my property. When talking to several pool companies, I am getting most recommending a 420 or 520 Pentair. The 520 seems huge - do I need that large of a filter.
    I have an in ground saltwater pool that is approx 18000 gal. My pump is 1hp.
    I must make a decision very soon. Any advice is greatly appreciated.

    JR
    1) 10,000 Gallons
    2) Cartridge Filter
    3) IG
    4) Pebble
    5) Hayward NorthStar Self Priming pump and a Hayward Swimclear Cartridge Filter

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    JasonLion's Avatar
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    May 2007
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    Silver Spring, MD
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    Re: Must replace filter - getting differing size recommendat

    Welcome to TFP!

    You don't have to get a large filter, you could get by with a 150 sqft filter. But if you can afford it, you will be happier with a larger filter in the long run. The larger the filter the longer you can go between cleanings and the more efficiently the filter will filter. We always recommend getting the largest filter you have room for and can afford.
    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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    Re: Must replace filter - getting differing size recommendat

    Thank you for the quick response!

    With all things remaining equal, does a larger filter reduce flow? Am I right in assuming that the 420 will still be significantly oversized for my application?

    Thanks again!
    1) 10,000 Gallons
    2) Cartridge Filter
    3) IG
    4) Pebble
    5) Hayward NorthStar Self Priming pump and a Hayward Swimclear Cartridge Filter

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    Voodoo_Pool's Avatar
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    May 2011
    Location
    On the border AR/TN
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    Re: Must replace filter - getting differing size recommendat

    Welcome to the Forum!

    I think this thread may answer your concern about filter size affecting (or not) flowrate: hydraulics-101-have-you-lost-your-head-t915.html

    According to Pentair, the 420 and 520 are both rated the same so getting the bigger filter will allow more time between cleaning.

    As Jason stated, bigger is generally better with regards to filter sizing.

    Enjoy!
    22,000 gallons "L" shaped with spillway spa; Hayward 4820 DE; IG Vinyl; 2000 ppm salt; 50 ppm Borates; liquid chlorine; Polaris w/ booster; TF-100 Test Kit w/SpeedStir

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    Join Date
    Feb 2008
    Location
    Denton, TX
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    Re: Must replace filter - getting differing size recommendat

    The 420 should be plenty for a pool your size. It's a great filter by the way.

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    Re: Must replace filter - getting differing size recommendat

    Great info! Thanks for the quick and informative replies.
    1) 10,000 Gallons
    2) Cartridge Filter
    3) IG
    4) Pebble
    5) Hayward NorthStar Self Priming pump and a Hayward Swimclear Cartridge Filter

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    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: Must replace filter - getting differing size recommendat

    Using a larger filter increases the total flow rate just a little because the larger filter has less total resistance to water flow. More importantly, since the water is spread out over a much larger filter area, the amount of water passing through any given patch of filter fabric is moving much more slowly and that allows the filter to catch finer debris that a smaller filter would catch.
    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

  8. Back To Top    #8

    Re: Must replace filter - getting differing size recommendat

    Awesome. The 420 is being installed today. Thanks again for the great and timely info. It got a little overwhelming with so many pool "professionals" offering different recommendations.
    1) 10,000 Gallons
    2) Cartridge Filter
    3) IG
    4) Pebble
    5) Hayward NorthStar Self Priming pump and a Hayward Swimclear Cartridge Filter

  9. Back To Top    #9

    Re: Must replace filter - getting differing size recommendat

    Quote Originally Posted by johnnyringo
    Awesome. The 420 is being installed today. Thanks again for the great and timely info. It got a little overwhelming with so many pool "professionals" offering different recommendations.
    I installed a 420 this spriing...I love it !!!!
    22,000 Gal, in-ground ,vinyl. Pentair Intelliflo VS, Clean&Clear 420 cartridge, Hayward NG 300K heater, Polaris, EasyTouch,IC-40, (former Baquacil - converted to SWCG)

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