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Thread: When to backwash DE when filtering a really dirty pool?

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    Join Date
    Aug 2007
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    Northeastern Ohio
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    When to backwash DE when filtering a really dirty pool?

    While filling my pool for opening, my well pump started sucking up dirt overnight. Now my pool is a lovely shade of brown.

    I have my DE filter going, and we've been bumping about once an hour (the pressure rises 10psi in that time). My manual tells me I need to backwash "when the gauge pressure rises more than 10 psi (.70 Bar) in less than a 24 hour period". Obviously when filtering a really dirty pool, I would imagine this doesn't apply (otherwise I would've backwashed about 10 time now!)

    How do I know when I truly need to backwash this thing?
    ~30000 GAL In-Ground 26'x50' Kidney Shaped Pool
    Hayward EC-75 DE Filter w/1.5HP Hayward SuperPump
    daily user of JasonLion's Poolcalculator
    (12) 2x10 SunGrabber Solar Panels...now if only there was some sun to shine on them!

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    Join Date
    Apr 2008
    Location
    Central Texas
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    I backwash mine when the pressure is 8-10 PSI higher than when it was last backwashed. I've noticed that the flow rate drops considerably as the filter backpressure rises.
    26,000 Gallon Gunnite IGP
    2 HP Challenger High Head Pump
    60sf Nautilus DE filter
    Polaris 280

  3. Back To Top    #3
    JasonLion's Avatar
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    May 2007
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    Silver Spring, MD
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    37,879
    You need to backwash when the pressure doesn't go down enough after bumping, say when you are getting less than 4 psi back after bumping. Typically that is much sooner than 10 bumps.
    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

  4. Back To Top    #4

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    Jul 2007
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    If the pool is truly dirty, it's possible that you will need to backwash several times or more in a short period. If the pressure goes up 8 or 10 pounds, then it's telling you the filter is holding enough dirt to slow the flow and it's time to backwash. Some people, when first filtering a really nasty pool will have to backwash 2 or 3 times in 6 or 7 hours.... so read your gauge and watch the flow.
    My Pool - 18x24 fully setup Cabana, 22x48 gunite/quartz plaster (3-5-3 depth) & 8' spa w/ spill and 5' natural rock waterfall; Hayward DE filter/pumps/heater; Hayward Pro Logic controller; Phantom cleaner. Finished 06/01/07.

    RedishConstruction.com

  5. Back To Top    #5

    Join Date
    Aug 2007
    Location
    Northeastern Ohio
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    178
    Thanks for the replies!
    ~30000 GAL In-Ground 26'x50' Kidney Shaped Pool
    Hayward EC-75 DE Filter w/1.5HP Hayward SuperPump
    daily user of JasonLion's Poolcalculator
    (12) 2x10 SunGrabber Solar Panels...now if only there was some sun to shine on them!

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