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Thread: Normal FC loss?

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    jasnovanorder's Avatar
    Join Date
    Jul 2015
    Hamilton Michigan

    Normal FC loss?

    What is a normal average amount of daily FC loss? Last night I raised my FC up to 10ppm. After vacuuming. Checked it a little while ago and it's down. So I checked for CC and a double check of the CYA Tonites tests results were
    FC 7
    CC 0
    CYA 50

    the pool sees most of the mid day sun I would guess about 5-6 hours worth. Is a 3ppm loss with a 50 CYA about average
    Intex AG metal frame vinyl sides 10,400 gal. 3000 gph intex pump with 16" sand filter
    My Slam

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    Mod Squad Texas Splash's Avatar
    Join Date
    Jun 2014
    South-Central Texas, Marion/San Antonio

    Re: Normal FC loss?

    Depending on your location, CYA, etc, normal FC loss is around 2-3. If you ever have additional doubt, you can raise your FC to SLAM level and perform an Pool School - Perform the Overnight FC Loss Test (OCLT). But I think for now you're good. If you have any more questions or concerns, you can always post a full set of test results for us to review. Have a nice evening.
    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
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    Richard320's Avatar
    Join Date
    Jan 2010
    San Dimas, CA (LA County)

    Re: Normal FC loss?

    2 to 3 FC per day is pretty normal.

    You lose a percentage to sunlight, not a fixed PPM. So at higher FC levels, you lose more. That's why you can't just dose the pool three days in advance. It's not a fixed amount. The recommended levels take that into account. Overchlorinating just leads to higher UV losses. If you lose 3 per day, and minimum is 4, target 7 or 7.5, not 10.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Join Date
    Apr 2013
    North OKC Area

    Re: Normal FC loss?

    When you say you raised FC to 10ppm last night, is that based on Pool Math or did you test 30min-1hr after adding chlorine?

    2-4 ppm FC loss is normal, the more sun, the higher the loss. The higher above the target FC level, the faster it is lost because you have extra chlorine that is not bound to CYA. Your CYA is 50, the target is 6ppm FC in the Chlorine/CYA chart. I would drop your target FC from 10 to 7 and see how much you lose by tomorrow. Do today's test after your chlorine addition has mixed for 30 minutes at least, possibly even stir with a leaf net since the OEM Intex pool circulation isn't very good.
    17,100 Gal 27' x 52" AGP steel wall vinyl; 44gpm Cooper sand filter; Hayward 1hp sp1580 single-speed; 1.5" plumbing, 1 skimmer/jet, inline chlorinator.
    Chlorine / CYA Chart | SLAM Process | Chlorine cost/fl. oz calculator

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