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Thread: Losing FC in direct sunlight

  1. Back To Top    #1

    Join Date
    May 2012
    Location
    Allentown, PA
    Posts
    219

    Losing FC in direct sunlight

    FC 9
    PH 7.6
    CYA 65
    CH 80
    salt 2300
    CC .5

    If my pool is covered all day it is fine, but when I pull the solar cover and leave the pool exposed to the sun I'm losing a whole lot of FC. Yesterday morning 7AM FC was 14.5, in late evening it was 9 FC. The SWG ran 12hrs. at 70% and it is oversized. I preformed the OCLT test and it passed with no problem. I had algae about 3 weeks ago, and I slammed the pool, and kept it at slam level for several days and passed the OCLT test then. Water looks nice and clear right now. My guess is algae, but why am I passing the OCLT? Could there be anything chemically that would cause this?
    21,500 Gallon Vinyl liner pool Eastern Pennsylvania
    Hayward 2 HP pump 2" Pvc pipes Full Sun Pool
    Hayward sand filter, Compupool CPSC 48 SWG
    12mil solar cover and reel

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    TFP Guide

    cowboycasey's Avatar
    Join Date
    Jul 2013
    Location
    Fletcher, OK
    Posts
    3,346

    Re: Losing FC in direct sunlight

    the only thing i see is your CYA is a little low at 65 ( probably 60), maybe take it to 70 or 80 and see if it will hold better. also your FC is high for a swg, you should be around 7 (pool school is down so I am not 100% positive on that number) with your FC number up over 10 it will lose more during the daylight hours.
    Pool: Intex 16x32 15000 gal, 2 speed 340042, Pentair CC320 Filter, CircuPool SJ45 Salt System, Intermatic PE653RC; Hot Tub: 650 Gal SWG Megachlor
    links: pool school * Recommended-Levels * SLAM * CYA chart * Test kits * How To Post Pictures * Poolmath * OCLT ** Support your website if we helped you :) **

  3. Back To Top    #3

    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,082

    Re: Losing FC in direct sunlight

    For an SWG, the FC minimum is roughly 5% of the CYA level so 4 ppm at 80 ppm CYA. This is a minimum so at the low point of the day in the morning just before the SWG turns on. You likely need to target higher so that it never gets below the minimum.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

  4. Back To Top    #4

    Join Date
    May 2012
    Location
    Allentown, PA
    Posts
    219

    Re: Losing FC in direct sunlight

    Okay thanks for the help. I am going to pull the cover off today and watch the numbers closely. I believe 3-10 FC is what is recommended by tfp with SWG and Vinyl. Thanks
    21,500 Gallon Vinyl liner pool Eastern Pennsylvania
    Hayward 2 HP pump 2" Pvc pipes Full Sun Pool
    Hayward sand filter, Compupool CPSC 48 SWG
    12mil solar cover and reel

  5. Back To Top    #5

    Join Date
    Jul 2014
    Location
    Hope Mills, NC
    Posts
    556

    Re: Losing FC in direct sunlight

    With the now 17 consecutive days over 90 degrees we are having, I had to uncover the pool (water temp hit 96 on top) and noticed a big drop in my FC as well. I doubled my SWG output time from 20% to 40% yesterday after discovering that I was hovering around the 2.0 FC mark. I quickly added 3/4 gallon of bleach as directed by pool pal and am at 6.5 FC as of 9:00 last night.

    I will check it when I get home from work, but I can only hope that it stays above 3.0 mark. Also really low on water, 2 more days forecast above 90.

    My numbers are very close to the OP's except I have 3000 ppm salt.
    16 x 32 17500 gallons
    Vinyl in-ground
    Hayward 250# Sand Filter
    1 HP Pump
    Hayward SWG

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