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Thread: Filter pressure increase prior to backwashing

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    Join Date
    Mar 2017
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    Houston, Texas
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    Filter pressure increase prior to backwashing

    Greeetings, I note your recommendation to backwash when pressure increases to 25% of the clean filter pressure. Is that advice valid for older pools (1980) with smaller plumbing? I have 2 return lines from the pool - main drain and skimmers, and both are 1.5" PVC. The return to pool line is a single 1.5" PVC. My furthest skimmer and main drain are about 60ft from the return manifold.

    Is it simply energy efficiency driving the recommendation for newer pools, or is also a consideration of potential tears for DE filter grids. My filter manufacturer recommends a 10psi increase prior to backwashing.

    Thanks,
    Regards,
    Greg2Cycle

    27000 gals / in ground / plaster/ spa / in-line tab chlorine / DE filter 60 sq-ft / polaris 380 with booster / 1.25HP single speed pump / 2 Mechanical switches / Houston, Texas

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    mas985's Avatar
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    May 2007
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    Re: Filter pressure increase prior to backwashing

    Welcome to the forum!

    The recommendation is good for all pools independent of age or setup.

    The old 10 PSI recommendation meant people were waiting until there was over 23' of extra head in the filter which would significantly reduce flow rates. In some pools with smaller pumps, 10 PSI is not even possible so the PO would never clean the filter and eventually flow rate would stop all together. So we came to an agreement that 25% would represent a smaller increase in the head loss and would tend to avoid these situations.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Mod Squad Jimrahbe's Avatar
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    Re: Filter pressure increase prior to backwashing

    Greg,

    The 25% increase rule is pretty conservative so that it can cover a wide range of filters, pool types, and plumbing differences.

    If you have been using the 10 pound rule and it works for you... use it.

    That said, I never backwash the two pools I have with DE filters. I break them down and clean them twice a year. I can do that because they both have variable speed pumps that run pretty slow most of the time. Normal PSI for them is 3 or 4 pounds.

    Thanks,

    Jim R.
    Finished in 2015 - 17K Gal, IG, 20' x 25' Almost Rectangular Pool, Pebble finish, three rockport water falls. Pentair Equipment: EasyTouch 4, IC40 SWG, 3 HP VS Pump, CCP520 Cartridge Filter.
    TF100 with SpeedStir and SampleSizer, ColorQ Pro 7, Dolphin Premier Robot Cleaner, added Screen Logic 2, added small 3 person Caldera Spa.

  4. Back To Top    #4

    Join Date
    Mar 2017
    Location
    Houston, Texas
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    Re: Filter pressure increase prior to backwashing

    Thanks for the advice. I've been using 8 psi recently, as waiting for 10 psi sometimes resulted in tears/leaks in the DE grids. My filter started at 16psi after backwash, so I will take it to 21 psi (~30%). Hopefully the lower dP will allow the grids to last longer. Typical service life seems to be about 3 years for the grids under current operating conditions,
    Regards,
    Greg2Cycle

    27000 gals / in ground / plaster/ spa / in-line tab chlorine / DE filter 60 sq-ft / polaris 380 with booster / 1.25HP single speed pump / 2 Mechanical switches / Houston, Texas

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