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Thread: Should I raise my CYA level?

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    plucky71's Avatar
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    Should I raise my CYA level?

    I'm trying to figure out this CYA level thing. Right now my CYA is at 35. It is within specs recommended on this site. But I do get direct sunlight from sun up to down, so maybe I should have it higher as it is recommended for full sunlight?

    And I am also wondering about chlorine use in regard to efficiency. With higher CYA my target FC raises. But does that mean that with higher CYA the FC used by the pool will decrease or change at all?

    So should I raise my CYA, and if yes what is the benefit?

    Here are my current test results:

    FC 7
    CC .5
    pH 7.4
    T/A 70
    CH 250
    CYA 35
    Temp. 84

    Thanks for the help!
    Outdoor fiberglass inground 15,000 gallons, Clean & Clear Plus 420ft. sq. filter, 1 h.p. WhisperFlo pump, New water cycler automatic chlorinater(not using), 1996 pool, TF-100 test kit.

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    JasonLion's Avatar
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    Re: Should I raise my CYA level?

    Your CYA level is fine where it is for now, but it will tend to drift down over the course of the swim season. Since you want it to be at least 30 at the end of the season, you will need to raise it at some point, and now is as good a time as any. The normal approach is to raise CYA to 50 in the spring, so it will still be at least 30 in the fall.

    Higher CYA levels require a higher FC level, but you actually need to add less total chlorine to maintain that higher level because the higher CYA level protects the chlorine from sunlight more effectively. The disadvantage is that higher CYA levels make it more difficult to fight algae, though this is not a big deal in the 30 to 50 range, it becomes important as CYA goes above 50.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    svenpup's Avatar
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    Re: Should I raise my CYA level?

    The appropriate CYA level is a balance between sun protection and chlorine effectiveness.

    With CYA too low, the sun will burn off enough chlorine during the day that FC falls below minimum (or maybe even to zero).

    With CYA too high, it becomes difficult to shock because of the high FC level needed.

    The guideline CYA levels here are high enough to protect FC from the sun and ensure residual sanitizer in the water throughout the day, but not so high that shocking is impossible.

    What level you chose within the guideline range is a judgement call based on your pool specifics including amount of sun exposure, and latitude.

    If your overnight loss is acceptable (<1.0) but you find that you are losing a lot of FC throughout the day you can raise the CYA. You should find that with higher CYA you lose less FC throughout the day and your overall chlorine demand may go down even though your target level is higher.

    The downside if you go too high is if you ever let the FC drop below minimum and algae does take hold you will have extremely high shock levels and shocking will be difficult.
    TFP Method Advanced Intermediate
    • 17,500 gallons - In Ground - Plaster - Hayward Swimclear 3020 Cartridge Filter - Sta-Rite Max-E-Glas Main Pump upgraded with A.O. Smith B2980 E-Plus New Centurion Two-Speed Motor - Polaris 280 Cleaner with Polaris PB4-60 Booster Pump - TightWatt2 Timer - Taylor K-2006 Test Kit - Pool Pilot Digital Nano SWCG

    Helpful Links: Pool School, BBB for Beginners, How to Shock (hint...it's a process not a product), Chlorine/CYA Chart, Jason's Pool Calculator

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    plucky71's Avatar
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    Re: Should I raise my CYA level?

    Thank you both for the excellent and helpful answers. That does give me a better understanding of the Chlorine/CYa relationship. I think I will raise my CYA level now, or over a period of time. I have two bags of shock plus, which I believe are di-chlor. I would like to use them up and get rid of them. Can I slowly use them to maintain my FC level and at the same time raise my CYA level? For example, add 1/4 or 1/8 of a bag, circulate, test FC and repeat the next day.
    Outdoor fiberglass inground 15,000 gallons, Clean & Clear Plus 420ft. sq. filter, 1 h.p. WhisperFlo pump, New water cycler automatic chlorinater(not using), 1996 pool, TF-100 test kit.

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    svenpup's Avatar
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    Re: Should I raise my CYA level?

    Quote Originally Posted by plucky71
    ...Can I slowly use them to maintain my FC level and at the same time raise my CYA level? For example, add 1/4 or 1/8 of a bag, circulate, test FC and repeat the next day.
    Absolutely! The TFP method doesn't preclude the use of pool store products, but rather promotes knowing what you are adding and why you are adding it.

    Use the pool calculator "Effects of adding chemicals" section to estimate the amount of CYA that will be added and keep track so you don't overdo it.
    TFP Method Advanced Intermediate
    • 17,500 gallons - In Ground - Plaster - Hayward Swimclear 3020 Cartridge Filter - Sta-Rite Max-E-Glas Main Pump upgraded with A.O. Smith B2980 E-Plus New Centurion Two-Speed Motor - Polaris 280 Cleaner with Polaris PB4-60 Booster Pump - TightWatt2 Timer - Taylor K-2006 Test Kit - Pool Pilot Digital Nano SWCG

    Helpful Links: Pool School, BBB for Beginners, How to Shock (hint...it's a process not a product), Chlorine/CYA Chart, Jason's Pool Calculator

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    plucky71's Avatar
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    Re: Should I raise my CYA level?

    Thank you! I did as you suggested and just added some of the di-chlor I had on hand.
    Outdoor fiberglass inground 15,000 gallons, Clean & Clear Plus 420ft. sq. filter, 1 h.p. WhisperFlo pump, New water cycler automatic chlorinater(not using), 1996 pool, TF-100 test kit.

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    Re: Should I raise my CYA level?

    Quote Originally Posted by JasonLion
    The normal approach is to raise CYA to 50 in the spring, so it will still be at least 30 in the fall.

    Higher CYA levels require a higher FC level, but you actually need to add less total chlorine to maintain that higher level because the higher CYA level protects the chlorine from sunlight more effectively. The disadvantage is that higher CYA levels make it more difficult to fight algae, though this is not a big deal in the 30 to 50 range, it becomes important as CYA goes above 50.
    This is exactly what I was looking for! I need to crunch my #s, but what I'm noticing (from memory) is that when my CYA was 90-95, 2 seasons ago I was burning up about 5ppm on a sunny day w/ swimmers. Targeting 11ppm and dosing up to around 16ppm at night. Last season my CYA was 65 and I set my target for 7, I recall losing around 3.5ppm on sunny days w/ swimmers. The past few sunny days with a CYA of what I estimated to be 45 (re-test I got 40) I was also losing 3.5ppm.

    I start thinking about how the +/- 10 ppm accuracy could put me at 30. If my target was 4 and I dosed it up to 8, losing 3.5 would put me at 4.5. I don't want to assume that my CYA test was -10 from my result. After seeing this post I will add 10ppm CYA and target 6. Hopefully my average consumption is closer to 2.5-3.

    Note: plenty of debris/leaves are falling in, I wouldn't be too surprised if that could account for some measurable loss.
    Aaron
    [ Vogue Vectra 24' AG | Hard plumb: Hayward Power-Flo Matrix 1HP 2-speed, 27" sand filter & Pentair MiniMax 100 NG | Taylor K-2006 | Central IL ]
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    Re: Should I raise my CYA level?

    Speedo-
    not to barge in on this thread, but I'm in Central Illinois as well. Curious as to where your Cl started out and ended up with your CYA = 45. My CYA is the same and I'm still trying to figure out if the pool is loosing a bit too much Cl daily or not. Thanks.
    30000 gallon inground gunite pool
    Intelliflo ic-60 SWG, pentair tagelus sand filter, 1.5 hp whisperflo pump, tf 100 test kit,
    2 kids(tl), 1 mini-dachshund/lab mix(t),
    Central Illinois

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