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Thread: Question about rain

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    daytoman's Avatar
    Join Date
    Jun 2013
    Oklahoma City / OK

    Question about rain

    And algae growth...

    Right now pool is setting at:
    Perfect numbers. However, it rained heavy last night and added a few inched to my 25K gal pool.

    This morning I added a half gallon of 6% because of the rain. Pool was clear, I did not test FC this morn, just had to head out to work. I got the numbers above this evening.

    However, there is a little bit of light coat of green in some areas of the shallow end and on the slopes of the deep end.

    What do you think I should raise FC to in order to keep this at bay?

    Finished my first SLAM about 2 weeks ago, passed OCLT. Its been crystal clear since. So this happens right after the rain. This is my first rain since starting trouble free pool system, so I just need to confirm what to do next.

    IG Lazy L configuration over 20 years old.
    25K gallons.
    Vinyl liner 10 years old
    Sand filter
    Marathon 1.5hp pump

  2. Back To Top    #2
    Smykowski's Avatar
    Join Date
    Sep 2011
    Gurnee, IL (North Suburban Chi-town)

    Re: Question about rain

    I would take it to the high end of the range and see what happens. It might just be debris blown in during the rain. A properly chlorinated, clean pool (which is what yours sounds like) should not at all be affected by the rain. There are several of us that divert rainwater from our roofs for free fillups.
    33' round, 23,000 gal AG vinyl , 1HP 2spd PowerFlo Matrix downsized with 3/4HP impeller (X2), Hayward S180T 150# sand filter (X2), Hayward H250 NG heater Pool Store year 1 - $850 for 2 months; Pool Store year 2 - $440 for 2 months, TFPC year 1 - $170 for 4 months; TFPC year 2 - $95 for 4.5 months
    The most important article on this site - The ABCs of Pool Water Chemistry

  3. Back To Top    #3

    TFP Guide
    mrcarcrazy's Avatar
    Join Date
    Jan 2014
    Odessa, TX

    Re: Question about rain

    What's your daily FC drop?
    According to:

    You don't want your FC to drop below 3. This is key, Rain itself doesn't cause Algae growth, low FC allows it.. At times large amounts of rain (on a pool with borderline FC) can drop you below the minimum...then you get the dreaded green crud.

    I had 3" of rain one day, but I had my FC at the top end of the spectrum, this made me safe and sound. Keep yours at the higher end and you should be fine....if not a quick SLAM will kill it off if you've kept on your feet with the levels.
    IG gunite/plaster pool/spa Started 1/17/14, Plastered 5/16/14
    Size: 12'-21'x39' free form, depth ranging from 4' to 7, attached 6 person spa with spillover.
    Equipment: Whisperflo 2hp pump, Pentair 30" sand filter, Pentair Mastertemp 400k BTU heater, 1hp Whisperflo for waterfalls, and a blower for spa floor

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