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Thread: High FC/CYA and health

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    Aug 2015
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    High FC/CYA and health

    I have a 3 years old daughter with multiple allergies, eczema with very sensitive skin. I am a first time pool owner and worry about high chlorine level in my pool. Any health risk in high chlorine level pool? My FC was 16 and CYA was 100 when I checked it. I believe high FC is needed due to such high CYA.
    I am wondering if high FC reqirement for my pool poses any potential risk for my daughter. Do you guys recommend partial draining to lower the CYA, which will allow lower FC level to be effective?
    Or does it even matter if high FC will be bound by such high CYA, to cause any trouble (that is if I understand it correctly) other then maintain my pool?

    Any advice regarding pool and health will be appreciated.
    Thank you guys.
    13k gal / IG / plaster / DE filter

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    Texas Splash's Avatar
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    Re: High FC/CYA and health

    Min, you can expect a more thorough and scientific explanation later than what I'm about to give you, but basically you are correct. With a higher CYA, the higher FC is safe and tied to that CYA. It's for those who far exceed the FC limit based on CYA, or have no CYA, that can subject themselves to unneeded levels of FC. As long as you follow the principles noted here in the Pool School - Chlorine / CYA Chart, you should be fine.

    Keep in mind however that whenever we say our CYA is 100, there's always a chance it is a bit higher. So at some point in the future you might be better served to lower that CYA. If nothing else, just so you can be certain that you are maintaining the correct FC for that specific CYA.
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
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    Re: High FC/CYA and health

    With 16 ppm FC and 100 ppm CYA, 99% of the FC is bound to CYA and is essentially innocuous simply holding the chlorine in reserve but not being active. At most it has oxidation power equivalent to 0.1 ppm FC with no CYA and virtually no disinfection capability so generally we ignore the chlorine bound to CYA. The chlorine unbound to CYA has the same concentration as a pool with only 0.16 ppm FC and no CYA so is low.

    As for the level of FC you need, IF your CYA is truly 100 ppm and not higher, then you don't want the FC to go below 8 ppm. 16 ppm would be higher than necessary unless your CYA is actually higher than 100 ppm.

    The only place where the FC level itself becomes relevant is if you were to drink the pool water, but even there you would have to drink extremely large quantities daily to be an issue. The EPA drinking water limit of 4 ppm FC presumes drinking roughly 2 quarts of water every day for a lifetime and this is with a factor of 100 safety factor relative to animal experiments to get to the highest No Observed Adverse Effect Limit (NOAEL). So basically you shouldn't worry about even the higher FC. The salt level in the pool is probably more hazardous in terms of increasing one's salt intake.

    If your pool is truly only 1900 gallons as indicated in your signature (i.e. if that's not a typo where you meant 19,000 gallons) then I would recommend you doing a partial drain/refill to lower the CYA level. It's easier to manage the pool at a lower CYA level especially if for whatever reason the chlorine level got too low and algae developed. Doing a SLAM at higher CYA levels requires extraordinary amounts of chlorine. You should probably shoot for around 50 ppm CYA to be more manageable. Then you would manage your FC to not go below 4 ppm.
    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"

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    Re: High FC/CYA and health

    Min, bleach baths are a common recommendation by dermatologists for eczema - your pool will be lower ppm than a bleach bath would be. I wouldn't worry.


    15k gal IG plaster w/ water feature; 600 gal spa w/ spillway; Pentair VS+SVRS Pump; Pentair FNS Plus DE Filter; Pentair MiniMax NT Heater; Rainbow Lifegard 320 In-Line Feeder (no idea what this does or how it works); Polaris 3900 Sport Cleaner (constantly on its side); Compool Lx3800 Control System; TFT-100 test kit.

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    Re: High FC/CYA and health

    Based on the Mayo Clinic recommendation for an eczema bleach bath, a half cup of 8.25% bleach in 40 gallons would be 67.5 ppm FC though with the higher resulting pH of around 8.4 (assuming an initial TA of 80 ppm) the active chlorine level is equivalent to 15.6 ppm FC at pH 7.5 so is over 150 times higher than what we use in our pools.
    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"

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    Re: High FC/CYA and health

    I can say from personal experience that since I started swimming/bobbing in our pool, my plaque eczema is healed. Even the scarring is looking better.
    Bob - Palm Beach by San Juan Pools. approx 5000 gals., Pentair 320 cartridge filter (all new guts installed by me), Goldline SWG, 'New to me' Kreepy Krauly Sand Shark, Intermec 104 Timer Test kit: TF-100 w/Speed Stir

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    Re: High FC/CYA and health

    Thank you so much for the replies. I am so much relieved now. Thank you guys!!

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