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Thread: When to backwash sand filter if pressure never goes up?

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    When to backwash sand filter if pressure never goes up?

    I know it's recommended to backwash a filter when the pressure rises a certain psi above the psi when the filter is clean - the psi rise caused by dirt/debris in the sand interfering the flow.

    However, my pressure hasn't risen in the two months since I've opened the pool. (I don't have an extremely dirty pool (no leaves, twigs etc., just some dirt/dust/pollen and the usual dead bugs/worms).

    Should I just forget about backwashing until the end of the season, or should I backwash after a certain amount of time 'just because'? I recall reading somewhere that the effectiveness of a sand filter actually increases as it gets dirtier (I guess up until there's too much dirt for proper flow).

    Thanks.
    16x28 Roman, 55000 litres, salt water, Zodiac Duoclear 130 (mineral cartridge removed!!!), inground, vinyl liner
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    duraleigh's Avatar
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    Re: When to backwash sand filter if pressure never goes up?

    I would only backwash when I saw the pressure rise.

    Good idea to do it at the end of the season just before you winterize, too.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    JasonLion's Avatar
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    Re: When to backwash sand filter if pressure never goes up?

    The only thing to watch out for is the possibility that your pressure gauge is broken. As long as the filter pressure doesn't go up and the water flow from the returns is fine, then don't worry about it. But if the water flow from the returns goes down, then backwash the filter even if the gauge hasn't gone up.
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    Re: When to backwash sand filter if pressure never goes up?

    Well I had a problem were a blockage/air caused my pressure to decrease thus masking my need to backwash when normally the pressure gauge would be sky high. I tested my theory by opening the drain to my filter just to check color which was green. You lose very little in a check process. If your going to do this make sure you bleed the pressure prior to trying to open this will make it possible to open the drain plug. Then bleed off the air after you reattach the drain plug.

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    Re: When to backwash sand filter if pressure never goes up?

    Quote Originally Posted by JasonLion
    The only thing to watch out for is the possibility that your pressure gauge is broken. As long as the filter pressure doesn't go up and the water flow from the returns is fine, then don't worry about it. But if the water flow from the returns goes down, then backwash the filter even if the gauge hasn't gone up.
    Gauge is OK. It's a glycerin filled good quality gauge. Pressue goes to zero when pump is off. 22 when pump is on and solar off, and 27 when solar comes on. 22 is the reading after freshly backwashed by the way (like when opening and closing the pool).

    Thanks.
    16x28 Roman, 55000 litres, salt water, Zodiac Duoclear 130 (mineral cartridge removed!!!), inground, vinyl liner
    Hayward Tri-star VS900 (1.85 HP) pump, Hayward C3030 cartridge filter
    Nine Techno Solis 4x10 solar panels, Jandy LX 250 natural gas heater
    Jandy Aqualink PDA with Sub Panel Power Centre

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    Re: When to backwash sand filter if pressure never goes up?

    You usually want to see a 20-25% increase from the "clean" pressure before you backwash.

    It's an old thread but it didn't have the answer.
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