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Thread: Air under sand filter valve.

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    Air under sand filter valve.

    I have noticed that once I started filtering a lot of the live algae and the pressure would rise it would sound like I have air under the valve on the filter, and this wouldn't stop until I did a deep cleanse of the sand in the filter. Now that I am not filtering a lot of live algae I still get air under my valve and my pressure doesn't seem to rise. Today for instance, the filter ran for five hours and didn't raise one pound in pressure. Thought it might be the gauge so I picked up another one and it still seems to not be rising. When valve is in backwash, or circulate I do not hear the sound of air under the valve, I do hear it a little when it is on rinse. I do not have any air bubbles in the basket at the pump, just a few tiny ones but it has always been like that. I thought that it may not be able to pull in enough water so I slightly opened the floor drain as well as and still the same. Any ideas?

    Also, just to be certain, the PSI should raise as the filter gets dirty correct? Is there any situation where I would not be able to trust the reading on the pressure gauge?
    24000 Gallons
    Cristal-Flo Hi-Rate Sand Filter
    IG - Vinyl
    3/4 HP Pump, and 44 Flow Rate
    Older than 10 years.

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    duraleigh's Avatar
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    Re: Air under sand filter valve.

    If you have air in the filter, it is virtually always a suction side leak. They are hard to find but you are sucking air somewhere between your skimmer and your pump.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Mod Squad jblizzle's Avatar
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    Re: Air under sand filter valve.

    We recommend backwashing when the pressure rises 20-25% over the clean pressure. For a properly sized filter and a clean pool, this may take many months for the pressure to rise a few psi ... so seeing no rise in 5 hours is not surprising. Unless your pool is not clear, in which case you should see a rise.
    Jason, TFP Moderator
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  4. Back To Top    #4

    Re: Air under sand filter valve.

    No, it hasn't cleared completely. I can see the floor in the shallow end and a little of the floor as it slopes toward the deep end. It is a blueish gray color and appears to being clearing more and more daily. Just concerned because the pressure doesn't rise as I thought it would.
    24000 Gallons
    Cristal-Flo Hi-Rate Sand Filter
    IG - Vinyl
    3/4 HP Pump, and 44 Flow Rate
    Older than 10 years.

  5. Back To Top    #5

    Re: Air under sand filter valve.

    Ill see if I can find a leak somewhere. Could it be something that would make the pressure in the filter read inaccurate? I just want to make sure there are no worries with too much pressure building in the tank.
    24000 Gallons
    Cristal-Flo Hi-Rate Sand Filter
    IG - Vinyl
    3/4 HP Pump, and 44 Flow Rate
    Older than 10 years.

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