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Thread: Cellulose fiber in DE filter

  1. Back To Top    #1

    Join Date
    May 2016
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    Albuquerque, NM
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    Cellulose fiber in DE filter

    Hi All,

    I have a few questions regarding Cellulose fiber replacement in a DE filter.

    I have a Pentair FNS+ 60 DE filter in which I'm using a Cellulose fiber replacement. Every 3 or so weeks my filter pressure runs high and backwashing becomes futile. As time goes on, backwashing seems to remove less and less while the Cellulose fiber becomes clumped and attached to the grids. I've read a lot of the posts on this forum but I wanted to double check, is the recommended solution to this problem just to do a full clean of the filter and recharge it fully? Is there no known way to prevent the cellulose fiber from clumping in the filter? Finally, how often should someone have to backwash or, in this case, perform a full clean?

    Thank you!
    16K freeform gunite with spa; Pentair FNS Plus 60 DE filter; Pentair 2 HP.

  2. Back To Top    #2
    JoyfulNoise's Avatar
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    May 2015
    Location
    Tucson, AZ
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    11,588

    Re: Cellulose fiber in DE filter

    Cellulose fiber degrades from chlorine exposure. It forms a sticky mass that is more difficult to remove than dirty DE and so the recommendation is to backwash more frequently. Also, unlike the pool industry, TFP recommends backwashing a filter once the pressure rises 25% above clean pressure. We also recommend you annually tear down your filter and deep clean it.

    How often have you been backwashing? Why do you not use DE?

    My Pentair DE filter is relatively oversized compared to my pool volume and so I found I only needed, at most, to backwash 2-3 times per year. Because my backwashing was so infrequent I have since switched to just doing two full tear-downs per year and I don't bother backwashing anymore. This actually saves me a lot of unnecessary water use (waste) and saves me on DE (20 pounds of DE per year).

    If your backwashing, based on a 25% filter pressure rise, is as infrequent as mine was, then you could go back to DE and just do two filter tear downs per year and forget backwashing altogether. Up to you.
    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

  3. Back To Top    #3

    Join Date
    May 2016
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    Albuquerque, NM
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    Re: Cellulose fiber in DE filter

    I think my Pentair is also oversized for my pool, from a full-clean/recharge my filter will have no appreciable change in pressure for 3-4 weeks. I usually backwash once I achieve that magic 25% that I read about here (so usually when I achieve about 22 from a start of 19). This can take several weeks.

    I've actually performed 2 deep cleans on my filter this season.
    1) The start of the season because the previous owner didn't
    2) Midseason when I noticed that my pressure was not decreasing due to clumping

    This will be the third time I perform a deep clean to get rid of all the clumps. I assume that 3-4 weeks was enough from the start to midseason to have the cellulose fiber degrade? At this rate, should I probably either backwash early even without that magic 25% or just not backwash and be prepared to perform deep cleanings when I notice the pressure increases enough?

    I use Cellulose mainly because of my kids being around and my pets and I don't want them to accidentally get into the DE.

    At this rate, next season, I would probably need 2-3 tear downs due to deterioration of the Cellulose Fiber.
    16K freeform gunite with spa; Pentair FNS Plus 60 DE filter; Pentair 2 HP.

  4. Back To Top    #4
    JoyfulNoise's Avatar
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    May 2015
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    Re: Cellulose fiber in DE filter

    Well, the choice of DE or cellulose is certainly your personal decision. Cellulose, in my opinion, seems to put a lot more stress on a filter (higher pressures, constant backwashing, ruined grid fabric, etc) than actual DE does. Personally I have no issue with DE safety and the risks of it are way overblown. Yes, it is an inhalation hazard but the exposure limits of it are all based on constant, 8-hr OSHA exposure studies, i.e., people who work around the stuff as part of their jobs and are exposed on a daily basis over decades. Charging up a pool filter two or three times a year hardly qualifies as the same level of exposure. Again, the choice is yours but if all you're worried about is your kids getting into it, then my personal opinion is DE is the least of your worries when it comes to pool chemicals.

    If you choose to stick with the cellulose fiber then I think you should just forget about backwashing and just plan to tear down your filter several times per season.
    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

  5. Back To Top    #5

    Join Date
    May 2016
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    Albuquerque, NM
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    Re: Cellulose fiber in DE filter

    Thanks for your expertise! I really appreciate it. I think for the rest of the season I'll continue with cellulose fiber but will definitely consider DE more in the future.
    16K freeform gunite with spa; Pentair FNS Plus 60 DE filter; Pentair 2 HP.

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