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Thread: DE Replacement After Backflush

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    DE Replacement After Backflush

    How much replacement DE should I be adding back into the system after I backflush? I've asked the same question of 5 different folks at the pool company that installed my pool and git 5 different answers. They told by neighbor (same pool installer) another answer altogether. Is there a good rule of thumb?
    23,200 gallon in ground pool, Vinyl Liner, Salt Water, Variable Speed Pump Intelliflow 3hp/1.32SF/3.96 SFHP, Filter Pentair FNS PLus DE FNSP36, Heater Pentair Mastertemp 250, SWG Jandy APURE35PLG, TF-100 Test Kit

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    harleysilo's Avatar
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    Re: DE Replacement After Backflush

    80% of the required amount posted on your filter on in the literature that came with your filter.

    4) At this point, you have removed ~ 80% of the old/ used DE so only add 80% of the DE you would use in a new or fully clean filter!!

    You can read more here: use-and-care-for-de-filters-t4086.html
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    Mod Squad jblizzle's Avatar
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    Re: DE Replacement After Backflush

    80% of the normal amount used after a full breakdown.

    What does the manual for your filter say?
    Jason, TFP Moderator
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    Re: DE Replacement After Backflush

    Owners manual is here http://www.pentairpool.com/pdfs/FNSPlusOM.pdf. Match up your model number to know how many square feet of filter area yours is.
    ~john
    24.5K G, pebble, SuperFlo VS 1.5, 48sq DE filter, Hayward H250FDN, Autopilot RC-52, Poolvergnuegen & 3 daily swimmers in season.

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    Mod Squad Bama Rambler's Avatar
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    Re: DE Replacement After Backflush

    There is a good rule of thumb and it's listed in the Use and Care of DE Filters article in Pool School. Basically it's 80% of a new fill and you should open the filter once a year and give it a good cleaning.
    Dave J. TFP Moderator
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    Re: DE Replacement After Backflush

    That helps. It looks like we have a 36 so according to the book it takes 3.6 pounds of DE at startup or 57.6oz. To replace 80% would be 46oz. I have a 12 oz scoop so it would take just under 4 scoops after backflush. That seems to make sense to me now. HOWEVER, as I was looking for the model number on the filter I found on the sticker it says Freshwater Only. I have a saltwater pool. Can that be right?
    23,200 gallon in ground pool, Vinyl Liner, Salt Water, Variable Speed Pump Intelliflow 3hp/1.32SF/3.96 SFHP, Filter Pentair FNS PLus DE FNSP36, Heater Pentair Mastertemp 250, SWG Jandy APURE35PLG, TF-100 Test Kit

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    Mod Squad Bama Rambler's Avatar
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    Re: DE Replacement After Backflush

    Yeah, that can be right.

    You don't truly have a saltwater pool. You have a freshwater pool with a little salt in it. When they warn against a "saltwater" pool, they're talking about an ocean water level salt.
    Dave J. TFP Moderator
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    Re: DE Replacement After Backflush

    Thank you. That made me panic.
    23,200 gallon in ground pool, Vinyl Liner, Salt Water, Variable Speed Pump Intelliflow 3hp/1.32SF/3.96 SFHP, Filter Pentair FNS PLus DE FNSP36, Heater Pentair Mastertemp 250, SWG Jandy APURE35PLG, TF-100 Test Kit

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    harleysilo's Avatar
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    Re: DE Replacement After Backflush

    LOL isn't learning all this stuff fun! How long have you had your pool? Have you taken your DE filter apart and cleaned it yet? Did you note the clean pressure on the filter so you'll know when to backwash again?
    18'x43' Sport Pool
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    Richard320's Avatar
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    Re: DE Replacement After Backflush

    Quote Originally Posted by harleysilo
    LOL isn't learning all this stuff fun! How long have you had your pool? Have you taken your DE filter apart and cleaned it yet? Did you note the clean pressure on the filter so you'll know when to backwash again?
    Good point! You don;t know if the filter looks like this inside.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
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    Re: DE Replacement After Backflush

    I took it apart a week and a half ago and gave it a very good cleaning. I now have a good idea of what the clean pressure should be so knowing when to actually backflush should be a little more clear.

    As far as the age of our pool it's new this summer and the process with the installer has been extremely painful. Started the install last September and were still working out issues as of this week. I could write a paper on all the issues we've had. If I had a magic rewind button I probably wouldn't have done it to be completely honest. I've never seen an industry so full of incompetence in all my life. I know that's a sweeping generalization but where I live it's definitely the case.
    23,200 gallon in ground pool, Vinyl Liner, Salt Water, Variable Speed Pump Intelliflow 3hp/1.32SF/3.96 SFHP, Filter Pentair FNS PLus DE FNSP36, Heater Pentair Mastertemp 250, SWG Jandy APURE35PLG, TF-100 Test Kit

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    Re: DE Replacement After Backflush

    Quote Originally Posted by Aspfam
    I took it apart a week and a half ago and gave it a very good cleaning. I now have a good idea of what the clean pressure should be so knowing when to actually backflush should be a little more clear.

    As far as the age of our pool it's new this summer and the process with the installer has been extremely painful. Started the install last September and were still working out issues as of this week. I could write a paper on all the issues we've had. If I had a magic rewind button I probably wouldn't have done it to be completely honest. I've never seen an industry so full of incompetence in all my life. I know that's a sweeping generalization but where I live it's definitely the case.

    Not really. It seems the case all over, and the amount of misinformation and lack of knowledge is truly staggering sometimes.
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