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Thread: Strange filter behavior

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    stev32k's Avatar
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    Mar 2009
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    Mobile, Alabama
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    Strange filter behavior

    When clean my inlet filter pressure is 10 psi and I usually backwash when it hits 16 psi. After backwashing I add 1.5 cups of DE to bring the pressure up to 11 psi. Several days ago the inlet pressure was up to 15 psi when the pump turned off for the day. The next morning when the pump came on the inlet pressure was 11 psi? I watched it off and on all day and the pressure slowly came up to 15 psi before the pump shut down after 8 hours. Next morning when the pump started the pressure was again 11 psi and came up to 15 after 8 hours before shutting down.

    This scenario has been repeated 4 days in a row - pressure rises to 15 then after setting overnight it is 11 psi the next morning. The gauge is fairly new seems to be working. I believe the 11 psi number because the polaris 280 cleaner moves around like it is getting adequate flow. At 15 psi it moves much slower.

    The filter seems to be working like it should because the water is clear as clean glass. Anyone have any ideas what could be going on?
    20' x 40' IG with vinyl liner volume approx. 35,000 gal.1.5 H.P. main pump, Polaris 280 cleaner W/ 3/4 H.P. booster pump
    Hayward sand filter, 3.14 sq ft, 62 gpm. Stenner 45 MPH10 chlorine feed pump. 1 micron final filter bags (home made and very effective)

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    JasonLion's Avatar
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    May 2007
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    Re: Strange filter behavior

    This is probably a side effect of having DE in the filter. While the flow rate is uniform, the DE slowly settles down, spreads out, and starts collecting debris, which builds up into a dense mat that partially blocks the flow. But when the pump turns off, the DE and debris shifts around and regions develop with no DE and no debris. The next time the pump is turned on, the DE again slowly spreads out and covers up the entire surface of the sand.
    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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    stev32k's Avatar
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    Re: Strange filter behavior

    The DE is the only thing I could think of, but I always add the DE to a 5 gal bucket of water then stir well and pour in about half - add more water, mix, and pour the remainder. So I should be getting a uniform coating, but maybe something happened the last time.

    I just vacuumed up some fine deposits and the filter pressure came up 3 psi to 14 psi. I then shut off the pump and let it set for about an hour. When I turned the pump on the pressure was down to 11 psi. I should do a really good study and find out exactly what is happening. Maybe I could get a patent on the "Never Backwash Filter" LOL.
    20' x 40' IG with vinyl liner volume approx. 35,000 gal.1.5 H.P. main pump, Polaris 280 cleaner W/ 3/4 H.P. booster pump
    Hayward sand filter, 3.14 sq ft, 62 gpm. Stenner 45 MPH10 chlorine feed pump. 1 micron final filter bags (home made and very effective)

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    Join Date
    Jul 2010
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    Philly
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    Re: Strange filter behavior

    Same thing happens to me when I add DE to my sand filter. Once I shut the pump off, even for just a few seconds, the pressure drops back to the original clean pressure.
    Bill
    18'X4' 7600 Gal AG
    3/4 HP Pentair Pump
    Hayward S166T 100 lb sand filter

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    Vette's Avatar
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    Jul 2012
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    Re: Strange filter behavior

    Quote Originally Posted by stev32k
    I just vacuumed up some fine deposits and the filter pressure came up 3 psi to 14 psi. I then shut off the pump and let it set for about an hour. When I turned the pump on the pressure was down to 11 psi. I should do a really good study and find out exactly what is happening. Maybe I could get a patent on the "Never Backwash Filter" LOL.
    That's called cartridge Although when they need cleaned with more than just a hose they can be a pain.
    11,700 gallon 21' round 54" deep all-resin AGP - June 2012
    Waterway 1HP 2-speed pump / 100 sq ft cartridge filter
    Hayward 150,000btu Natural Gas heater
    I use and recommend the TF-100 for testing

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