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Thread: Backwashing DE Filter

  1. #1
    Junior Member speyedr's Avatar
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    Backwashing DE Filter

    Howdy all!

    I am opening my pool this weekend. Got my DE filter up and running and added the appropriate amount. I have a mesh cover so the water is more 'swamp' than I would like but it is clearing quickly. Of course, with the clearing comes the rising filter pressure and I am sure I will need to backwash in the next day or so, hence my question.

    When I backwash my DE filter it removes some of the DE, is this correct? If so, how do I guesstimate how much to add back?

    I am sure I will have more questions as I move forward, but this one is really messing with my head at the moment.

    Thanks!
    Pool: 800sqft, 21k gal free form plaster IG; Intellichlor SWG; Delzone EC2 Ozone; Pentair FNS+ 48sqft DE filter; Pentair Master Temp 400k BTU heater
    Spa: Premium Leisure MarkIII Millenium 350gal portable spa w/ ozone

  2. #2
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    Re: Backwashing DE Filter

    When backwashing, the general rule of thumb is to only add 1/4-1/3 the amount of D.E. you would normally add after your filter has been cleaned. This will all be based on what size D.E. filter you have.

  3. #3
    Junior Member speyedr's Avatar
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    Re: Backwashing DE Filter

    Quote Originally Posted by Pacifica
    When backwashing, the general rule of thumb is to only add 1/4-1/3 the amount of D.E. you would normally add after your filter has been cleaned. This will all be based on what size D.E. filter you have.
    Great, thanks for the quick reply!
    Pool: 800sqft, 21k gal free form plaster IG; Intellichlor SWG; Delzone EC2 Ozone; Pentair FNS+ 48sqft DE filter; Pentair Master Temp 400k BTU heater
    Spa: Premium Leisure MarkIII Millenium 350gal portable spa w/ ozone

  4. #4
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    Re: Backwashing DE Filter

    I've heard to replace 2/3 to 3/4, never as low as 1/3. The spec for mine is 4.5 lb, so after a backwash I add 3 lb.
    --paulr
    BBB "Intermediate Swimmer"
    IG plaster pool 18.5K gal, Hayward Pro-Grid DE filter, 3/4 HP Hydramax II; Polaris 380, 3/4 HP booster
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  5. #5
    Mod Squad Butterfly's Avatar
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    Re: Backwashing DE Filter

    Hi speyedr and welcome to the forum

    Do you have an owner's manual for your filter?
    TFP Moderator -TF100 Test Kit - TF100 TestKit YouTube Channel- PoolMath- Pool School -
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  6. #6
    Administrator JasonLion's Avatar
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    Re: Backwashing DE Filter

    Waste, the local DE filter expert, suggests adding 80% as much after backwashing. See this post for a through description of the entire process.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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  7. #7
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    Re: Backwashing DE Filter

    Every manual that I am familiar with says to add the same amount as the intitial start up after backwashing. More is safer. You don't want any portion of the grid assembly uncoated, especially if you have live algea or any other contaminates. .

  8. #8
    Junior Member speyedr's Avatar
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    Re: Backwashing DE Filter

    Quote Originally Posted by Butterfly
    Hi speyedr and welcome to the forum

    Do you have an owner's manual for your filter?
    Thanks! Been lurking since I started my new pool last spring. You folks have all been great help (indirectly) and I have yet to need pool store 'advice' (if you can call it that) or a pro. Thank you all very much.

    I have the owners manual (model is in my sig) but I could not find anything specific on replacing DE after backwash, though I will double check.

    I am sure glad I asked.
    Pool: 800sqft, 21k gal free form plaster IG; Intellichlor SWG; Delzone EC2 Ozone; Pentair FNS+ 48sqft DE filter; Pentair Master Temp 400k BTU heater
    Spa: Premium Leisure MarkIII Millenium 350gal portable spa w/ ozone

  9. #9
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    Re: Backwashing DE Filter

    The written procedure should be on the side of the filter if you can read it.

  10. #10
    Junior Member speyedr's Avatar
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    Re: Backwashing DE Filter

    After thoroughly reading the entire manual it seems that Pentair assumes that the owner will either:

    1 - Clean the filter manually by opening the unit and hosing the filter elements down in place

    2 - Clean the filter manually by disassembling the filter elements and hosing them down individually (once a year is enough for me thanks!)

    3 - Backwash using a separation tank, which I don't have.

    #3 is the ticket thought since it is backawashing. They instruct the owner to backwash til the water runs clean and then replace all of the DE.

    I have to say that I have been in the Computer Industry in one form or another all of my professional life, or close to 20 years now, and it's about time I followed my own advice. RTFM.

    Thanks all, for helping me help myself.
    Pool: 800sqft, 21k gal free form plaster IG; Intellichlor SWG; Delzone EC2 Ozone; Pentair FNS+ 48sqft DE filter; Pentair Master Temp 400k BTU heater
    Spa: Premium Leisure MarkIII Millenium 350gal portable spa w/ ozone

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    Re: Backwashing DE Filter

    We have a Hayward DE installed last year. The instructions are to backwash until clear, rinse until the sight glass is clear, and refill with 4.5 lbs of DE (going from memory on amount here). The amount of DE is the same whether initially filling it or backwashing it. Of course, that's just this unit - I wouldn't doubt that others are different, so YMMV.
    29,000 gal. vinyl in-ground mountain lake (freeform); Hayward DE filter, 2 skimmers, Aquabot, Nature 2 (retired); LoopLoc winter cover, Pool installed March 2009... Added 2 - 4 X 20 Fafco Solar Bears with Goldline control and AutoPilot SWG in 2010

  12. #12
    Administrator JasonLion's Avatar
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    Re: Backwashing DE Filter

    It is nearly impossible to backwash all of the DE out of a DE filter. DE is going to accumulate in the filter unless you either do a through clean out at least occasionally or use slightly less DE than you use on an initial fill. We are constantly getting people posting pictures of DE filters totally clogged with DE when they finally clean them out after a couple of years.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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  13. #13
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    Re: Backwashing DE Filter

    Quote Originally Posted by JasonLion
    It is nearly impossible to backwash all of the DE out of a DE filter. DE is going to accumulate in the filter unless you either do a through clean out at least occasionally or use slightly less DE than you use on an initial fill. We are constantly getting people posting pictures of DE filters totally clogged with DE when they finally clean them out after a couple of years.
    For Example



    1981, 25K, IG, Blue Plaster 1996, somewhat oval, widens a bit at shallow end, 1.5" pipes, 2" at Pad, 1 separate main drain, 1 skimmer, 4 returns + dedicated cleaner return, 10 ft deep end with very fast decline from shallow, Pentair Quad 80 DE, Pentair Intelliflo VF, 3/4 HP Booster Pump (equipment pad about 8 ft below top of pool), Challanger 3/4 Trash/Emergency Pump 120v, Polaris 280 (pressure), iRobot Verro cleaner (robotic), Aquabot Turbo (robotic), Jacuzzi Tracker 4X (vacuum) Pool Blaster (Buster), Two (2) PoolSkims, Solar Breeze (solar powered top skimmer) (beta to ver. 2, release date 2010), ColorSplash LED replacement bulb. Aries 550 gal separate spa, 2002 (our 3rd and BEST spa) , BBB-Bromine

  14. #14
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    Re: Backwashing DE Filter

    Quote Originally Posted by JasonLion
    It is nearly impossible to backwash all of the DE out of a DE filter. DE is going to accumulate in the filter unless you either do a through clean out at least occasionally or use slightly less DE than you use on an initial fill. We are constantly getting people posting pictures of DE filters totally clogged with DE when they finally clean them out after a couple of years.
    Is it safe to say that if pressure stays in the normal range that DE is not accumulating to levels that would clog it? The reason I ask is that I'm going on the third year without taking the filter apart and filter pressure is still the same as when I took over. I do use a skimmer sock and backwash very thoroughly each time...
    20K gal IG plaster pool, Manually chlorinated with 6% bleach, 1.5 HP Sta-Rite Dura-Glas II pump, Pentair FNS Plus 48 DE filter, Polaris 280

  15. #15
    Administrator JasonLion's Avatar
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    Re: Backwashing DE Filter

    I strongly recommend opening up a DE filter and doing a through cleaning at least every other year (at the very minimum), and preferably more often.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    TFP Admin. Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  16. #16
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    Re: Backwashing DE Filter

    I took mine apart & cleaned it at the end of last season & plan to do so each year... It really didn't take all that long - the hardest part was making sure all of the "vanes" properly lined up when putting the top back on. It satisfied my OCD tendencies and gave me a chance to see what was going on in there. Plus then I knew exactly where I was starting from for the next season.
    29,000 gal. vinyl in-ground mountain lake (freeform); Hayward DE filter, 2 skimmers, Aquabot, Nature 2 (retired); LoopLoc winter cover, Pool installed March 2009... Added 2 - 4 X 20 Fafco Solar Bears with Goldline control and AutoPilot SWG in 2010

  17. #17
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    Re: Backwashing DE Filter

    I always take my DE filter apart and hose the grids clean when I have a pressure rise. The whole process takes about 30 minutes at most. IMHO, backwashing only and re-chargeing with fresh DE when you don't know how much old DE was flushed out is a gamble at best. The whole point of a DE filter is that the DE forms a thick coat that sticks to the grids really well. Backwashing does not remove much DE at all. Then most people recharge with 75% of the volume required for a full charge. You just backwashed out 25% of the old DE and replaced it with 75% new DE. That is how you end up with elements so packed full with DE that you have to chisel it out!
    TFP Moderator
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  18. #18
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    Re: Backwashing DE Filter

    Quote Originally Posted by zea3
    I always take my DE filter apart and hose the grids clean when I have a pressure rise. The whole process takes about 30 minutes at most. IMHO, backwashing only and re-chargeing with fresh DE when you don't know how much old DE was flushed out is a **** shoot at best. The whole point of a DE filter is that the DE forms a thick coat that sticks to the grids really well. Backwashing does not remove much DE at all. Then most people recharge with 75% of the volume required for a full charge. You just backwashed out 25% of the old DE and replaced it with 75% new DE. That is how you end up with elements so packed full with DE that you have to chisel it out!
    I totally understand if you disagree with me, but I don't think you understand my point...

    In the end, I don't care how my filter is filtering as long as it is doing the job. If the DE was really building up inside the filter as you describe it, don't you think I would see a pressure rise at some point that would persist even after backwashing?

    Here is my thinking on the subject: At around $130, the filter grids are cheap to my mind. It seems reasonable to me that a person could pretty much run them until they clog, however long that takes, then instead of cleaning them simply throw them away! As I stated above I'm going on my third year with my current ones, and they are filtering as well as they ever did as far as I can tell, plus there has been no persistent pressure rise. Even if I could only get 3 years out of a set, I would be happy with that!

    However, I guess the only real way for me to know what is going on for sure is to take it apart once and see for myself...
    20K gal IG plaster pool, Manually chlorinated with 6% bleach, 1.5 HP Sta-Rite Dura-Glas II pump, Pentair FNS Plus 48 DE filter, Polaris 280

  19. #19
    Mod Squad zea3's Avatar
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    Re: Backwashing DE Filter

    Quote Originally Posted by Beez
    I totally understand if you disagree with me, but I don't think you understand my point...

    In the end, I don't care how my filter is filtering as long as it is doing the job. If the DE was really building up inside the filter as you describe it, don't you think I would see a pressure rise at some point that would persist even after backwashing?

    Here is my thinking on the subject: At around $130, the filter grids are cheap to my mind. It seems reasonable to me that a person could pretty much run them until they clog, however long that takes, then instead of cleaning them simply throw them away! As I stated above I'm going on my third year with my current ones, and they are filtering as well as they ever did as far as I can tell, plus there has been no persistent pressure rise. Even if I could only get 3 years out of a set, I would be happy with that!

    However, I guess the only real way for me to know what is going on for sure is to take it apart once and see for myself...
    You may not get the same type and amount of debris in your water that I get in mine. I have a huge oak tree on one side of the pool and a crepe myrtle on the other. These two trees drop leaves, blooms, pollen, pods, and twigs almost non-stop. Then there are the squirrels that think my pool is a giant trash can and drop half gnawed acorns and pine cones in the water. When my water is algae free and tree debris is light I can go about 6 weeks before I get a 10 pt pressure rise. I have tried the backwash and recharge method and the pressure rose again in about 2 days.
    If your method works for you that's great! For me it is a better investment of my time and money to break down and clean my filter rather than replace the grids every 3 years. I prefer my method, you prefer yours. Not really a case of agree/disagree but what works for a given situation.
    TFP Moderator
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    Vogue 21" round AG, Pentair 1 hp 2 speed pump, 36 sq ft DE filter, Upper Texas Coast

  20. #20
    Administrator JasonLion's Avatar
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    Re: Backwashing DE Filter

    The kind of clogging that appears in geekgranny's pictures would show up as a change in the "clean" filter pressure. But milder clogging would not always show up as a visible pressure change. Excess DE tends to fall to the bottom, where is stays out of the way of the great majority of the filtering process. Even though it is staying out of the way of filtering, it can still cause other long term problems. Sometimes the DE at the bottom will calcify and form sold blocks that are difficult to remove without causing damage. Other times it serves as an area with poor circulation, creating a place where organics can accumulate and cause lingering low level excess chlorine demand.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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