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Thread: How much FC loss is a concern

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    tedinelkgrove's Avatar
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    How much FC loss is a concern

    I realize my CYA is high (150ppm) and will drain pool after our guests leave. I use the pool calculator to determine how much liquid chlorine to add daily. I use a desired FC value of 15. Evey morning I test and results are ~ 11-12ppm. Is that a 3-4ppm a concisderable amount to lose, or nothing to worry about?

    I can't wait to drain the pool and bring CYA down to use a lot less chlorine.

    Thanks.
    ~15000 gallon inground, plaster pool
    Jandy CL460 Cartridge Filter Tank, Jandy Stealth SHPF 1.5hp pump, Pentair Legend II cleaner
    Leslie's DPD Complete Test Kit, TF Tests FAS-DPD Chlorine Test Kit
    Heliocol solar pool heating (HC-40 x6)

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    Mod Squad Bama Rambler's Avatar
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    Re: How much FC loss is a concern

    I usually loose 3 to 4 a day, CYA is 45. Pool is in full sun most of the day. Sun eats a lot of chlorine.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
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    Re: How much FC loss is a concern

    Quote Originally Posted by tedinelkgrove
    I realize my CYA is high (150ppm) and will drain pool after our guests leave. I use the pool calculator to determine how much liquid chlorine to add daily. I use a desired FC value of 15. Evey morning I test and results are ~ 11-12ppm. Is that a 3-4ppm a concisderable amount to lose, or nothing to worry about?

    I can't wait to drain the pool and bring CYA down to use a lot less chlorine.

    Thanks.

    It is my understanding you are talking about losing the 3-4ppm overnight?? If so...

    You should test at night, after the sun sets- 1 hour after lst added chlorine and turn off anything that adds chlorine (swg, chlorinator etc). Then test again in the am before the sun hits your pool. If it drops more than 1 ppm then something organic is using it up ( eg algae). This is the overnight Chlorine drop test. Don't just add the chlorine and guess at the 15ppm- test it.


    Here are directions on the overnight test: http://www.troublefreepool.com/pool-...rnight_fc_test
    18K gallon IG pool and separate 1200 Gallon IG spa - Both have: Diamond Brite Plaster- Hayward DE Filter -Propane heater- renovated 8/2008

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    JasonLion's Avatar
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    Re: How much FC loss is a concern

    With CYA around 150, losing 3 to 4 ppm of FC means something is wrong. The most likely cause is a low level algae problem.
    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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    tedinelkgrove's Avatar
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    Re: How much FC loss is a concern

    Thanks for the replies. I will try the overnight chlorine drop test. I have a feeling it is fine, but want to make sure and be proactive. I test in the mroning and add chlorine then. I don't test again until next morning. Since I get full sun, I would imagine the drop is result of sun. I'll post results overnight Cl drop tomorrow.
    ~15000 gallon inground, plaster pool
    Jandy CL460 Cartridge Filter Tank, Jandy Stealth SHPF 1.5hp pump, Pentair Legend II cleaner
    Leslie's DPD Complete Test Kit, TF Tests FAS-DPD Chlorine Test Kit
    Heliocol solar pool heating (HC-40 x6)

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    Re: How much FC loss is a concern

    I'm dropping 3 ppm a day, and that's with a clear pool cover.
    32'x16' vinyl in-ground. 8' Deep, 3' Shallow
    Est. 21,000 gallons
    Hayward 300lb Sand filter w/SP-0714T valve assembly.
    Hayward 1 1/2HP Super Pump swapped with a A.O. Smith Dual Speed Motor.
    1 Skim, 1 Drain, 2 Outlets

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    Re: How much FC loss is a concern

    Quote Originally Posted by Bama Rambler
    I usually loose 3 to 4 a day, CYA is 45. Pool is in full sun most of the day. Sun eats a lot of chlorine. :evil:
    You could try operating at a higher CYA level with a higher proportional FC level. Most people find that this reduces the absolute chlorine loss so in your case that might drop it to 2-3 ppm FC per day which is more typical.
    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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    tedinelkgrove's Avatar
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    Re: How much FC loss is a concern

    FC after dusk, 10.5
    FC this morning, 10
    ~15000 gallon inground, plaster pool
    Jandy CL460 Cartridge Filter Tank, Jandy Stealth SHPF 1.5hp pump, Pentair Legend II cleaner
    Leslie's DPD Complete Test Kit, TF Tests FAS-DPD Chlorine Test Kit
    Heliocol solar pool heating (HC-40 x6)

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    JasonLion's Avatar
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    Re: How much FC loss is a concern

    The overnight test didn't show any problem with organics/algae, so maybe that is normal for your pool. With a very high CYA level, FC loss to sunlight is usually quite low. If you have a lot of people swimming every day or a few people swimming for a long time, that could contribute to your FC loss.
    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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