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Thread: Dusty green/brown silt in pool help!

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    Dusty green/brown silt in pool help!

    I have a 15,700 gallon oval AG pool with vinyl liner. I have been using TFP methods and pool math with my TF-100 test kit. Thing going great since start up this year. Chemicals are spot on FC 1 PH 7.4 TA 100 CYA 30, I put recommended borax and bleach in like normal to bring levels to normal and the water is clear but there has been a fine "dusty, silt-like" film on the bottom stirs easily, not slimey or green. It will vaccum but takes forever and is back the next day. What is it? How do I get rid of it? Do I need to add clarifier or algecide. Please help!! I have a 1.5 hp 1speed sand filter, thank you

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    Mod Squad pooldv's Avatar
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    Re: Dusty green/brown silt in pool help!

    No clarifier and no algaecide. You need more chlorine. FC of 1 is too low for your CYA, FC/CYA Chart, FC must be kept above minimum at all times to keep the pool sanitary and algae free. When FC drops below minimum bacteria and algae will grow.

    This is how we kill algae, SLAM
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    Re: Dusty green/brown silt in pool help!

    Well, it's dead algae and your numbers are not "spot on". An FC of 1 is inviting algae into your pool and the algae has accepted your invitation.

    Pool School FC/CYA relationship chart tells you that your FC should be around 4 ppm but NEVER lower than 2 ppm.

    Your statement that you put borax and bleach in "like normal" is disconcerting. How often do you add Borax?

    Please read "The ABC's of Pool Water Chemistry" up in Pool School
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Dusty green/brown silt in pool help!

    I added my numbers in my original post to pool math and it said to add 81oz 8.25 bleach and 15oz borax. I did that and after 30+min I tested again and my FC is at 4. So maybe I just let the FC get to low thus allowing the silt material to grow? I do not regularly add borax this is only the second time that pool math has suggest a small amount of borax

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    Re: Dusty green/brown silt in pool help!

    The borax suggestion from pool math was either because you put a target for borates in or........it was because of a target for PH higher than your 7.4. Borates would be the last step in balencing clear water as an optional addition. I'm with the others above, time to read up a bit on your basics here: Pool School - ABCs of Pool Water Chemistry

    Your chlorine was too low and you likely do have the start of an algae bloom.
    18*36*23 true "L" vinyl IG 29,000 gallons. SWG. TF-100 test kit.
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    Re: Dusty green/brown silt in pool help!

    Your FC is too low, but it sounds to me like times I have seen a sand filter with a cracked lateral that is allowing small amounts of media to come into the pool.

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    Re: Dusty green/brown silt in pool help!

    That is not sand coming into your pool. Sand is gritty and goes immediately back to the bottom if stirred up. Yours "poofs" away when disturbed, right? That's dead algae.

    Your chlorine has been to low. I suggest you keep chlorine about 8-10 ppm for at least 48 hours and then let it come back down to about 4 ppm and keep it there. Vacuum the dead algae up into the filter each day and I think it will all go away.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Dusty green/brown silt in pool help!

    Ok thank you so much I will read the pool chemical section again, I didn't set any targets on pool math I just kept what was already entered for targets and entered only my results. Yes it "poofs" away when disturbed. No sand I will bring chlorine levels up to 8-10 for 48 h and vaccum hope this does the trick thank you!

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    Chasmengr's Avatar
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    Re: Dusty green/brown silt in pool help!

    All season long, about once a week I have been vacuuming up minor amounts of that silty stuff from the Styrofoam joints telegraphing through the liner. I have always thought it was decaying leaves or something; dead algae?. Never a bloom nor a SLAM.

    I'm religious about watching and logging my numbers:

    CYA = 50 (will target lower <after closing drawdown> during next spring startup)
    FC = 4.8 (last evening before adding to target 6.5)
    CC = 0.0 (last evening)
    TA = 50
    pH = 7.4 (last evening)
    salt (for eye comfort) = ~2500 (not tested, just added per PoolMath)
    Temp = 76F (last evening) (plan to buy solar cover & reel before next season)
    CSI = n/a (-0.93 per PooolMath)
    borates = 0
    CH = 160

    seasonal daily average FC demand ~3

    20160823_174455.jpg
    Chas & Cheryl (first-time, second-year pool owners)
    Radiant Metric Oval AGP 16'x32'x52"; Pentair: Clean&Clear 150 Cartridge, OptiFlo 1.5 Hp 2-spd, and 320C Feeder (all mounted below water level); Taylor K-2006 & SpeedStir; Maytronics Dolphin E10 (aka Einstein)
    installation pics (2015-2016)

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