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Thread: Backwashing my sand filter

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    BigEyesLittleWallet's Avatar
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    Aug 2010
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    Metamora IL
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    Backwashing my sand filter

    I have been sweeping the bottom of my pool and my PSI has been going uo about 10 PSI before sweeping is not longer effective. This is what I would expect. What is strange is that when I backwash the filter the water leaving does not look dirty at all. The pressure does drop. I did just get done rebuilding my multi-port value also. In the past I've always had very dirty looking water when backwashing. Should I be concerned.
    18'x45'x52"" AG Pool. (22,200 gals)
    Pentair Sand Dollar Sand Filter SD-60
    1.5 hp pump
    CompuPool Saltwater Chlorinator 26K Gallon CPSC24
    TF-100 Test Kit

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    duraleigh's Avatar
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    Sebring, Florida
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    Re: Backwashing my sand filter

    Should I be concerned.
    Well, that is a little unusual for sure. Your psi goes up so your filter is catching something. Your psi then goes down because the backwash flushes out what the filter caught.

    That should normally result in something you could see but I think I would continue......your filter is not lying to you....it's working.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    BigEyesLittleWallet's Avatar
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    Re: Backwashing my sand filter

    Now that the water seems to be cleaner I can see the bottom pretty well. The bottom of the pool looks like it has sand on it. I'm guessing this means I need to take the sand filter apart and look for broken laterals?
    18'x45'x52"" AG Pool. (22,200 gals)
    Pentair Sand Dollar Sand Filter SD-60
    1.5 hp pump
    CompuPool Saltwater Chlorinator 26K Gallon CPSC24
    TF-100 Test Kit

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    MJCP's Avatar
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    Sep 2007
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    Michigan
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    Re: Backwashing my sand filter

    Just a thought but,
    Whenever I troubleshoot any kind of problem, I always suspect the problem is associated with the "Last thing done" before looking for new causes.
    Make sure your rebuild of the Multiport didn't result in this problem.
    15x32 Lazy L Inground / Concrete - 20,000 US Gal 1979 build
    1.0Hp Maxiglass/ Sand Filter, 7th season with Pool
    Painted cement finish repainted 2011
    400,000 btu Pentair Master Temp NG

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    Join Date
    Apr 2013
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    North OKC Area
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    298

    Re: Backwashing my sand filter

    I would check the spider gasket and the gasket on the bottom of the multi-port that seals it to the stand pipe.

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