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Thread: Pentair DE Filter Grids

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    Pentair DE Filter Grids

    I have a Pentair FNS Plus 60 DE filter on my pool. I disassembled the grids today to do a manual clean/soak on the grids. Six of the eight grid frames were broke near the top of the return pipe. It has been one year since the filter was last manually cleaned. The last time it was cleaned I had to replace 4 broken/torn grids. None of the filter grids' cloth was torn this time. I normally have not done this maintenance, a pool proffessional has been doing it for me. After what I found today, maybe I should be doing this job myself. The bttom half of the filter house was about 30% filled with D.E. and the grids were packed with DE muck between the grids. I now know, from reading here on the forum, that I have been overcharging my filter w/ DE after a backwash. I should have been using only 5 scoops rather than the 6 required after a manual cleaning. But why are the frames breaking on my grids? I normally backwash after I see a about 5 psi delta from the initial pressure after backwashing. Is it normal for the grid frames to break like this? I assume it is necessary to replace the grids when you find a broken frame or is it? Do most of you manually clean your DE filters more frequently? Looking for your advice and experience.
    Thanks in Advance!
    Larry
    note; the grids are Unicel replacements.
    21,500 gal. IGP, Diamond Kote plaster, spa, and waterfall features, flagstone coping w/ flagstone/river pebble decking. Pentair NSFP 60 filter, 2-ea. 2 HP Whisper Flow pumps, 1-ea. 3/4 HP Hayward booster pump for Polaris 3900 cleaner, AquaLink RS6 controls, GoldLine SWG, T-15 cell

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    Re: Pentair DE Filter Grids

    When a filter calls for 6 scoops I only use 1.5, the reason is at the pool and spa show one year they had a filter designed so you can see the inner workings as they added earth, the first 2 scoops when through the filters and coated the fingers and the rest of the 4 scoops just collected at the bottom. I know it sounds crazy to go against what they say to use on the tank but I've been using 1.5 scoops when recharging after back washing and the pools stay clear so something has to be working.
    -Kevin
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    22,000 gal / 16' x 32' / Vinyl / Hayward s244t /Pentair SuperFlo 1 hp

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    kenmar's Avatar
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    Re: Pentair DE Filter Grids

    The first time I backwashed my DE filter, as soon as the water coming out of the backwash pipe turned "brown", I directed the flow to a large plastic tub. Then, over the course of a few days I let the solids settle, poured off the clear water, and dried the sediment.
    The remaining dried solids filled just under two DE (1 lb) scoops.
    Since then, I add 1 scoop after each backwash.

    The reason I did this was because my pool builder, told me it was not necessary to add DE after backwashing. Logic told me I must be losing some portion of the DE during backwasing.

    I know, I am very weird.
    20'x40' / 30,000 Gal / In Ground / Vinyl
    Pentair FNS 48 DE Filter / Pentair Challenger 1.5 HP Pump
    Jandy Lite2 400k BTU Propane Heater / Dolphin Dynamic cleaning robot
    TF-100 Test Kit / BBB
    Creator of SimplePool (BBB Friendly Android App) http://www.simplepool.net

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    Re: Pentair DE Filter Grids

    Yes, it does sound "weird or crazy" as you both say to only add 1-1.5 scoop after a backwash, but my "lying eyes" tell me your right. There must not be much DE removal during a backwash, because most of the new material was stacked out on the bottom of the filter case or clumped between the grids. I will try the reduced approach on the next backwash. It does make sense. It also appears that I should probably open the filter case more frequently and at least hose the grids to remove the majority of the old DE material, maybe twice a year?
    Thanks,
    Larry
    21,500 gal. IGP, Diamond Kote plaster, spa, and waterfall features, flagstone coping w/ flagstone/river pebble decking. Pentair NSFP 60 filter, 2-ea. 2 HP Whisper Flow pumps, 1-ea. 3/4 HP Hayward booster pump for Polaris 3900 cleaner, AquaLink RS6 controls, GoldLine SWG, T-15 cell

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    Re: Pentair DE Filter Grids

    Are you backwashing as per this thread?

    A complete backwash will get ~80% of the DE out of the filter. I certainly agree that if you only backwash for a minute or so, you're only gonna dump a couple pounds of DE - if you backwash the way I say to in the linked thread, you'll get a lot more out 8)

    Of course, the best thing to do is break the filter apart and manually hose the grids/ fingers (THANKS Waterbear for reminding me of that ) If you're pressed for time and don't have fill water issues, a complete backwashing will be fine, but you really should just clean the grids manually
    Luv& Luk
    -Ted

    Having done construction and service for 4 pool companies in 4 states starting in 1988, what I know about pools could fill a couple of books - what I don't know could fill a couple of libraries :-D

    POOL SCHOOL, TF Testkits, Jason's Pool Calculator, CYA vs. cl chart, (Just a few DARNED handy links!)

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    Re: Pentair DE Filter Grids

    Thanks for reposting your pearls of wisdom. I've been looking for that post. Yes, I do backwash as you describe in your post with the exception of the 1 minute filter cycle and repeating the backwash /rinse cycles. I usually lower the pool by ~ 8-10 inches on a normal backwash cleaning routine. I've been adding the DE through the skimmer as you describe, too. I have 2 other suction sources working concurrently. My pool store "expert" says that all the DE I see on the bootom of the filter case is picked back-up when circulating. There is no way in the world all the DE I observed is picked up by circulation, besides alot of it was in big clumps.

    On a side note, my education of pools was furthered this morning at the pool store. It turns out that most of my filter grids were not broken. Only one, and I know how that was broke, by me! I did not know that the main cross spars on the grid frame were supposed to be able to move and flex. I had puchased 7 new grids and took them home where I thought I had discovered that some of the new ones were broke. I returned to the store, where my "expert" explained that this was how the grids were constructed. Dummy me! Of course they would not let me return the new ones, which I had not installed yet. That was an expensive $250 lesson. The pool has been rather expensive this month with the conversion to borates, new pool sweep pump, and lots of acid and chlorine, etc. And I'm installing a Goldline SWG system in the next couple of weeks. This pool is beginning to feel like owning a boat!
    Thanks,
    Larry
    21,500 gal. IGP, Diamond Kote plaster, spa, and waterfall features, flagstone coping w/ flagstone/river pebble decking. Pentair NSFP 60 filter, 2-ea. 2 HP Whisper Flow pumps, 1-ea. 3/4 HP Hayward booster pump for Polaris 3900 cleaner, AquaLink RS6 controls, GoldLine SWG, T-15 cell

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    Re: Pentair DE Filter Grids

    Quote Originally Posted by Duk
    Thanks for reposting your pearls of wisdom. I've been looking for that post. Yes, I do backwash as you describe in your post with the exception of the 1 minute filter cycle and repeating the backwash /rinse cycles. I usually lower the pool by ~ 8-10 inches on a normal backwash cleaning routine. I've been adding the DE through the skimmer as you describe, too. I have 2 other suction sources working concurrently. My pool store "expert" says that all the DE I see on the bottom of the filter case is picked back-up when circulating. There is no way in the world all the DE I observed is picked up by circulation, besides alot of it was in big clumps.

    On a side note, my education of pools was furthered this morning at the pool store. It turns out that most of my filter grids were not broken. Only one, and I know how that was broke, by me! I did not know that the main cross spars on the grid frame were supposed to be able to move and flex. I had puchased 7 new grids and took them home where I thought I had discovered that some of the new ones were broke. I returned to the store, where my "expert" explained that this was how the grids were constructed. Dummy me! Of course they would not let me return the new ones, which I had not installed yet. That was an expensive $250 lesson. The pool has been rather expensive this month with the conversion to borates, new pool sweep pump, and lots of acid and chlorine, etc. And I'm installing a Goldline SWG system in the next couple of weeks. This pool is beginning to feel like owning a boat!
    Thanks,
    Larry
    21,500 gal. IGP, Diamond Kote plaster, spa, and waterfall features, flagstone coping w/ flagstone/river pebble decking. Pentair NSFP 60 filter, 2-ea. 2 HP Whisper Flow pumps, 1-ea. 3/4 HP Hayward booster pump for Polaris 3900 cleaner, AquaLink RS6 controls, GoldLine SWG, T-15 cell

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