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Thread: OK if CYA is below 30?

  1. #1
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    OK if CYA is below 30?

    My CYA has declined below 30 over the past week or so. I thought I was around 35 last weekend, but I guess the rain and filter cleaning took its toll. Anyway, I seem to have no problem holding chlorine, even on sunny days. Is there a need for me to boost the CYA to 30? I understand that I may have to do some guesstimating in terms of recommended FC levels, although I tend to shoot for the high end of the range. And if I had to shock, I could overshoot a little and assume a CYA of 30. I know recommended levels are 30-50, but if I can maintain chlorine in sunlight, why not go a little lower?
    33,000 gallon plaster pool
    Jandy L-Series -CL580 Cartridge Filter

  2. #2
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    Re: OK if CYA is below 30?

    I would say if you are able to maintain your FC leve with that CYA level leave it alone. Less cholorine additions you will have to do. But keep an eye on the CYA level since it is at the bottom of the recommended level fro non SWG pools
    13,000 Plaster IG Pool approx
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  3. #3
    Senior Member Isaac-1's Avatar
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    Re: OK if CYA is below 30?

    There is no technical problem with CYA levels all the way down to the bottom of the ability to read it on a test (20 or 30 depending on the view tube) as long as you can maintain FC levels with sunlight in your location. I assume your pool is mostly shaded.
    Indoor 20x40 36,000 gallon vinyl pool with 1.5 HP 2 speed Jandy FloPro pump, Hayward EC75 Perflex DE filter, 11 4x12 Techno-Solis panel roof top solar heat with Aquasolar controller, Dolphin Diagnostic Pro Robot Cleaner. Also LMI metering chlorine dispenser pump and soon to be connected UV Ozonator and now Hot Spring Jetsetter standalone spa
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  4. #4
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    Re: OK if CYA is below 30?

    Quote Originally Posted by Isaac-1
    There is no technical problem with CYA levels all the way down to the bottom of the ability to read it on a test (20 or 30 depending on the view tube) as long as you can maintain FC levels with sunlight in your location. I assume your pool is mostly shaded.
    Actually, I get a lot of sunlight. The weather has been on and off over the past week, with rain almost daily, but also a fair amount of sunshine. Yesterday, was almost entirely sunny at the pool, with one intermittent shower for 45 minutes.
    33,000 gallon plaster pool
    Jandy L-Series -CL580 Cartridge Filter

  5. #5
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    Re: OK if CYA is below 30?

    so how much chlorine are you losing daily? or should i say, how much chlorine are you adding on a daily bases?
    15,000 gallon inground fiberglass pool with spa. 350lb Sand filter, 1.5 hp pump, and heater

  6. #6
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    Re: OK if CYA is below 30?

    Quote Originally Posted by smooth2222
    so how much chlorine are you losing daily? or should i say, how much chlorine are you adding on a daily bases?
    When I was starting around 16-17, I was finishing around 11-12, which I thought was quite good for the amount of sunlight and considering I was starting so high. Yesterday, I started around 17.5 and finished at 14. Today, I was still at 12 at noon, and I hadn't added any chlorine yesterday or today.

    To answer your question, I was adding about 2 large jugs of Chlorox over the course of a day, which boosts my FC by almost exactly 5.
    33,000 gallon plaster pool
    Jandy L-Series -CL580 Cartridge Filter

  7. #7
    Mod Squad BoDarville's Avatar
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    Re: OK if CYA is below 30?

    The CYA in my pool is currently 28. I am intentionally erring on the side of running a bit low on my CYA. Even with a CYA of 28 in the full Texas sun, my FC drops from 4 to 2. Even at an FC level 2, I am in range for my CYA according to the Pool Calculator. I add an average of 96 oz per day of 6% bleach to bump the FC level to 4 after sunset. I have also run several OCLTthis season and have lost zero FC overnight at this CYA level.

    If your CYA is less than 30, I'm curious as to why you are running a chlorine level in the mid teens. This seems like overkill. Per the Pool Calculator, the target FC is between 2 and 6 for a CYA level of 30. You could save a lot of bleach my maintaining the FC at this level. Just to be safe, I would perform an OCLT to rule out any nascent algae or other organic contamination. If you pass the OCLT, then I would maintain an FC of between 2 and 6.
    TFP Moderator 26,680 gal Plaster IGP 3.5 - 10' depth / Attached Waterfall Spa, Manually Chlorinated, Triton Sand Filter, 1.5 HP * 1.1 SF = 1.65 SFHP 1-speed Pentair WhisperFlo WF-26 Pump, 400K BTU NG Teledyne Laars Series One Heater, Polaris 360, Test Kit Comparison, Chlorine/CYA Chart, SLAMing Your Pool, OCLT
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  8. #8
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    Re: OK if CYA is below 30?

    Quote Originally Posted by BoDarville
    The CYA in my pool is currently 28. I am intentionally erring on the side of running a bit low on my CYA. Even with a CYA of 28 in the full Texas sun, my FC drops from 4 to 2. Even at an FC level 2, I am in range for my CYA according to the Pool Calculator. I add an average of 96 oz per day of 6% bleach to bump the FC level to 4 after sunset. I have also run several OCLTthis season and have lost zero FC overnight at this CYA level.

    If your CYA is less than 30, I'm curious as to why you are running a chlorine level in the mid teens. This seems like overkill. Per the Pool Calculator, the target FC is between 2 and 6 for a CYA level of 30. You could save a lot of bleach my maintaining the FC at this level. Just to be safe, I would perform an OCLT to rule out any nascent algae or other organic contamination. If you pass the OCLT, then I would maintain an FC of between 2 and 6.
    I was shocking and treating the pool as if my CYA was 30, since that was around what I tested last weekend. I was trying to pass the OCLT and clear out the alagae that we had when we opened the pool. I only passed the OCLT on Thursday night. I will now run at a lower level.
    33,000 gallon plaster pool
    Jandy L-Series -CL580 Cartridge Filter

  9. #9
    Mod Squad BoDarville's Avatar
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    Re: OK if CYA is below 30?

    OK, now that makes sense. Sounds like you are on the right track
    TFP Moderator 26,680 gal Plaster IGP 3.5 - 10' depth / Attached Waterfall Spa, Manually Chlorinated, Triton Sand Filter, 1.5 HP * 1.1 SF = 1.65 SFHP 1-speed Pentair WhisperFlo WF-26 Pump, 400K BTU NG Teledyne Laars Series One Heater, Polaris 360, Test Kit Comparison, Chlorine/CYA Chart, SLAMing Your Pool, OCLT
    A good test kit is an investment, not an expense.

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