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Thread: Backwashing to Drain the Pool

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    Backwashing to Drain the Pool

    Real time help appreciated-

    I have a plunger valve going into a DE filter on my 35K gallon pool. The only way I have to pump water to waste is to pull the plunger valve and backwash the filter to waste. Can I backwash to waste for a few hours to drain the pool to accommodate a partial refill to lower my CYA? Should I remove the DE grids or does it matter?

    Assuming this is safe I'm going to start a drain/refill this afternoon. Going to use the main drain and a vacuum hose with the understanding that once I start draining I can't stop because I can't let the pump loose prime.

    If it's not safe I'm going back to the drawing board... can remove the plunger and use a few of these to stop up the plumbing in the right places?

    Trying to avoid a sump pump. The pool is going to be remodeled this fall and I'm going to make sure I have the ability to vacuum/pump to waste on the new pluming design.

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    Richard320's Avatar
    Join Date
    Jan 2010
    San Dimas, CA (LA County)

    Re: Backwashing to Drain the Pool

    Pull the grids and it will work. Run backwash for hours and any debris in the pool will end up embedded on the insides of the grids and ruin them.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Backwashing to Drain the Pool

    Thank you

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    Re: Backwashing to Drain the Pool

    Just a follow-up to anyone searching for info. Backwashing to drain the pool seemed to work okay. The pressure on the system was about 28 PSI while draining when my normal clean filter PSI generally runs at about 12 PSI. I haven't put the grids back into the filter- waiting for it to stop raining. The pool should be filled by mid afternoon and I'll get it started up.

    Make sure you tighten the band clamp on the filter really well. Mine popped off at one point. Fortunately the water level wasn't so low that I couldn't regain the prime on the pump, but it was close.

    I'll post water test results in the other forum tonight.

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    In the Industry
    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: Backwashing to Drain the Pool

    Richard320 brings up a VERY good point. backwashing is a little tough on either sand or DE so it is generally not a good idea to do it for hours. A longer than normal backwash is just fine but doing it as an everyday practice is not helpful.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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