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Thread: How do folks backwash?

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    Default Re: How do folks backwash?

    It sounds like you are looking for a discussion on the topic; there's probably enough traffic on TroubleFreePool for a discussion. Not sure about PoolSpaForum. You may want to register and post your ? on TFP.

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    Default Re: How do folks backwash?

    Okay - I didn't know about that site. This place is my go-to. Thanks.
    20,000 gallon plaster (concrete) pool
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    Default Re: How do folks backwash?

    Thanks, but there's a fair bit of traffic here from Google searchers, but very little from registered members . . . so not much new discussion. That's not something that will change before next spring, for a variety of reasons.

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    Default Re: How do folks backwash?

    Hi Ben,

    Can you explain why I should get such a large filter for a 20,000 gallon pool? I'm about to pull the trigger on something.
    20,000 gallon plaster (concrete) pool
    DE filter
    Nature 2 (unchanged)

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    Default Re: How do folks backwash?

    Oh, and because of the DWP rebate program, I'm going to install a Pentair variable speed pump.
    20,000 gallon plaster (concrete) pool
    DE filter
    Nature 2 (unchanged)

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    Default Re: How do folks backwash?

    • All filters function better with low flow rates per sft of filter area. This is ESPECIALLY true with sand filters.
    • All filters run longer between cleaning with low flow rates.
    • High flow rates tend to damage filters. High flow = high differential pressure which KILLS filter cartridges, especially modern 'high-capacity' cartridges with pleats that are too close together. High flow may damage DE membrane support grids. High flow WASHES SAND OUT of the filter during backwash, and PUSHES DIRT THROUGH the filter during operation on sand filters.
    • It is still possible to develop high differential pressure, across the media, with oversize filters but it's much less likely.
    Is that enough? If you need more, you'll have to wait till later this weekend.

    By the way, REGARDLESS of filter type or size, you need a WORKING pressure gauge to monitor filter ops properly.
    • NO FILTER should operate at over 30 psi absolute (unless it's the new-ish Pentair high-pressure sand filter).
    • NO FILTER should operate at more than a 7 or 8 psi pressure rise (clean to dirty). Cartridge filters should be cleaned at a 5 psi rise (old style) or 3 psi rise (new style with pleats too close).

  7. #17
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    Default Re: How do folks backwash?

    Thank you.

    If there's more to say, of course I want to know.
    20,000 gallon plaster (concrete) pool
    DE filter
    Nature 2 (unchanged)

  8. #18
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    Default Re: How do folks backwash?

    BTW, I've ordered the recommended filter, the Hayward C3070, and a Pentair Superflo VS. They'll be installed next Friday, September 6th.
    20,000 gallon plaster (concrete) pool
    DE filter
    Nature 2 (unchanged)

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    Default Re: How do folks backwash?

    I'll try to get back to this before Tuesday, but I'm glad. I hope it works out really well for you.

    One of the additional reasons for an oversize filter that I hadn't mentioned is the problem of VS pumps. Most of these pumps -- including the Whisperflo VS -- are actually extremely high volume 3HP pumps that can pretty much DESTROY most smaller filters if they are inadvertently run at full speed / full power! They ought to come with a key-locked maximum setting, based on the filter & piping they were matched to, so this couldn't accidentally happen.

    The Pentair Superflo VS is apparently 'just' a 1.5 HP pump (PLENTY large enough for a 20K gal pool!), so the problem is reduced. Even so, that pump can potentially generate nearly 40 psi, if driven against a dirty filter that is undersized!

  10. #20
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    Default Re: How do folks backwash?

    The pump and filter were installed yesterday, and so far they're working very well.
    20,000 gallon plaster (concrete) pool
    DE filter
    Nature 2 (unchanged)

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