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Thread: Sand filter pressure drop

  1. #1
    Senior Member guamguy's Avatar
    Join Date
    Feb 2010
    Location
    Guam, USA
    Posts
    387

    Sand filter pressure drop

    I've noticed something strange (maybe) with my sand filter. The other day, I vac'd the pool, afterwards I checked the filter pressure to ensure
    I didn't need to backwash. Pressure was up to about 28psi, clean filter is about 20. Looked again a few hours later, same 28 psi, so I didn't do anything, shut the pump off for the day. Today I started the pump, and pressure is down to 22 and holding, flow from the returns is good and strong, and the gauge is good (I tested it at work against a calibration standard). I've noticed this once or twice in the past, but is it normal for a sand filter to behave this way? All chemistry is right in line except for slightly high TA, and the water is crystal clear and sparkling. I do not have any DE in the filter right now, and seems to be filtering the water just fine.
    Have a great 4th of July weekend
    12,800 gallon IG plaster kidney-shaped pool, waterslide, 800 gallon spa.
    1HP 2 speed Sta-Rite pool pump, 1.5 HP Sta-Rite spa jet pump. 2 skimmers, 1 main drain
    Purex-Triton TR-60 325 lb.sand filter. 2" Plumbing, Intex SWCG, TF-100 test kit.
    Link to pics of my pool! http://www.troublefreepool.com/my-oasis-t26558.html

  2. #2
    Senior Member dmanb2b's Avatar
    Join Date
    Apr 2009
    Location
    NY
    Posts
    3,779

    Re: Sand filter pressure drop

    Chalk it up to a mystery...keep your eye on it from time to time and enjoy your 4th!!!
    24'x52" AGP (13,500 Gallons), Intex SWG, (2)Solar Bear 4x20 panels, Hayward S220T Filter, 1/2hp Pentair Superflo

    Pool School, TFTestKits, Pool Calculator

  3. #3
    Senior Member
    Join Date
    Apr 2007
    Location
    Raleigh, NC
    Posts
    19,827

    Re: Sand filter pressure drop

    same 28 psi, so I didn't do anything, shut the pump off for the day. Today I started the pump, and pressure is down to 22 and holding,
    My sand filter does something very similar but not as dramatic.

    From time to time my normal psi of 10 will climb to 12. It takes a while and it goes up smoothly so I feel like it is junk accumulating on the top of the sand bed restricting flow. Frequently, I can shut it off for just a few minutes, turn it back on and the psi has returned to 10.

    In my case (and perhaps yours) I think it is caused by dirt accumulating and layering the top of the bed. Then, when you shut it off or on, the resulting turbulence inside the filter breaks up and disturbs that very fine layer on the top and the resistance in the filter returns to normal.

    After all that, I think I like dman's response as well or better than mine!!
    Dave S.
    Site Owner
    TFTestkits owner
    TFTestkits , PoolMath , Pool School

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