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Thread: How often to backwash a sand filter?

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    How often to backwash a sand filter?

    I noticed that after a certain amount of time, like 1 day, my filter systems seem to "idle". It's still humming, and there's still water circulating through it, but it's not that strong. The first visible sign that it's what I call "idle" is that, if you look at the surface of the water, it's moving very little or not at all. The only way I've been able to "fix" it is to backwash, then it resumes full strength filtering/pumping.

    Was wondering if this frequency of needing to backwash is normal, or perhaps characteristic of the lower HP pumps. I experienced this even with my 2nd brand new pump that I just bought two days ago (Hayward Powerflo LX, 1 Hp)
    1) 10,400 gallons
    2) Sand filter
    3) Above ground
    4) Hayward Powerflo LX, 1 Hp

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    In the Industry


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    Re: How often to backwash a sand filter?

    If you are asking if back-washing daily is normal, then the answer is no. The frequency of back-washing will vary from pool to pool, based on bather load, debris falling into pool from nearby trees, etc. Keeping an eye on your pressure gauge is the best way to know when to backwash. How is your pressure on your filter? Do you know what your 'clean pressure' should be?

    Also, if you have water circulating through your filter, this sounds to me more like a pump issue. While this water is circulating, is your pump on?

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    Join Date
    May 2010
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    Re: How often to backwash a sand filter?

    watching the pressure on the gauge works. See what it runs at normally, and when its like 10psi higher than normal, backwash till its clear. You can also get a feel for when its time to backwash by just feeling the jets. When they are sputtering, its definately time to backwash. Either way works.
    Matt

    Hayward Pump 3/4 HP - brand new
    sta rite sand filter - not sure of size, i will get back to this
    20 by 40 inground pool, vinyl liner, 8ft deep end
    2 skimmers and a main drain.
    1 jet in the deep end, 1 jet in the shallow end.
    Live in New England = about 3 months of pool usage.

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    Re: How often to backwash a sand filter?

    To be honest, I never really used the gauge, nor am I sure what it "should" be. The only guidance I received on the pump/filter ... 12 years ago ... was that I might need to backwash this "once in a while", especially if the pool was dirty .... and to let if backwash until the water shooting out was "clean". So that's pretty much what I did for the last 12 years. At some point, I noticed that the pressure of water coming out of the jet was decreased ... and then I started backwashing at that time to cure the problem.

    Now that I got a new pump 2 days ago, I ran into the issue again within the first day. FYI I'm in the middle of converting from Baquacil to Chlorine so perhaps this needed backwash frequency with brand new pump and new sand will be temporary.
    1) 10,400 gallons
    2) Sand filter
    3) Above ground
    4) Hayward Powerflo LX, 1 Hp

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

    Re: How often to backwash a sand filter?

    Instead of the 10 psi increase Mattyssox suggested, we recommend backwashing when the pressure goes up 25% above the clean filter pressure.

    Baqua conversions will gunk up the filter fairly dramatically, so frequent backwashing is expected during a conversion.
    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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