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Thread: Random green spots on pool bottom and certain corners/crevices

  1. Back To Top    #1
    Prav's Avatar
    Join Date
    Nov 2010
    Miami, FL

    Random green spots on pool bottom and certain corners/crevices

    Hi, all...

    Been a while since I posted, but I have a question:

    I finally added SWG (with T-15 cell) to the pool (probably close to a year ago), but I find that I still have to add extra chlorine during certain times of the year.

    Even running the SWG at 100% almost continuously, there are certain places in the pool floor and corners (I'm guessing with poor circulation) where I do get what's definitely algae growth (what I can reach easily is slimy and does rub off/fade if I hold a tablet to it).

    Last time I tested (mid-last week daytime):
    FC - 6 (which tells me it was probably closer to 8 at sunrise and maybe falls to 4-5 by day's end)
    CYA - 80
    pH - 7.5
    Borates - 60
    Rest within "normal" parameters as per Pool School.
    Water temp - consistently >88 degrees, even pushing 90+
    Lots of debris/leaves, seedlings etc. from nearby trees. Pool is in direct sunlight from 9AM till about 5-6PM.

    No, I have not had time to do overnight test - last time I did a few months ago, things were clear up.
    No, I don't brush religiously every day - that might be the "quick fix" as it will stir things up and loosen potential growth before it takes hold - or, perhaps some of it.

    My questions:
    - does anyone find they have to SUPPLEMENT the SWG with liquid chlorine on a consistent basis? I would guess that if I got FC closer to 10-12 consistently, I would have less issues - but I can barely get to 6-8!
    - Besides the obvious "need to stay on top of it with continuous brushing" and "probably should shock/overnight test" (been there done that), what else can I do with my chemistry?

    14'x30' (est. 14K gal) w/spillover spa (est. 500 gal) - 1995 // Diamond Brite Blue Quartz - 2006
    Hayward SwimPure Plus T-15 - 2013 // Zodiac MX-8 - 2013
    Plain ol' Intermatic mechanical timer // Pump: 1 HP Pentair SuperFlo - 2012
    Filter: Hayward C17502(S) Cartridge Filter - 2011 // Heat Pump: Sunrunner/Aquapro 1300 (127K BTU) - 2011

  2. Back To Top    #2
    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Random green spots on pool bottom and certain corners/crevices

    A Hayward T-15 is designed for a 40,000 gallon pool. Unless you have a very short pump run time, it should be doing better than what you describe. It seems you have algae growing in the pool and need to manually SLAM the pool to clear out the algae before the SWG will be able to keep up on it's own. There is no reason to expect the SWG to be able to SLAM the pool on it's own.

    You need to SLAM the pool, see the instructions in Pool School. That is the only way to completely eradicate the algae and get things back to normal. So far you have help the algae back, but never killed all of it. Once it is all killed, it will have a very hard time coming back (as long as you maintain appropriate FC levels).
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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