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Thread: Pool School CL and Heater recommended levels

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    Pool School CL and Heater recommended levels

    So here's the thing. Pool school recommends 70 CYA and 5 ppm target FC. Hayward recommends 1-3 ppm of CL. If you're beyond 3 as pool school suggests are you not causing sanitizer damage to your heater? We know Hayward will say so. What level of FC is too much on a continual basis?
    16 X 32 Vinyl. Hayward aqua rite salt system, T -15 cell. Hayward H250 gas heater, Hayward 1HP superpump.

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    Mod Squad jblizzle's Avatar
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    Re: Pool School CL and Heater recommended levels

    Hayward is parroting old advice based on a CYA level of 0. The CYA greatly buffers the aggressiveness of the FC. Low pH is much much worse for the heater than high FC.
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    Re: Pool School CL and Heater recommended levels

    The EPA says you need 1ppm to 3ppm FC in your drinking water for it to be safe. No manufacturer is ever going to say otherwise.

    3ppm FC with no CYA is roughly 1.5ppm hypochlorous acid - depending on temperature, PH, etc. etc.

    20ppm FC with 70ppm CYA is roughly 0.19ppm hypochlorous acid. Significantly less.


    If you assume Hayward's equipment is meant to operate on an indoor pool with CYA at 1ppm HOCL - you can run 45ppm FC at 70ppm to achieve the same HOCL levels (not that you ever want to or need to)
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    Re: Pool School CL and Heater recommended levels

    I would love to see a conversion or way to calculate the amount of available hypochlorous acid VS CYA. I also am leery of running my FC at 8-9(my CYA is 50-60) I tried to let it come down to 4-5 and sure enough pool got a little cloudy so back to 9 and within a day its clear. Didn't realize that CYA has that much of a buffering effect.
    Location Charlotte NC. Pool is a IG vinyl liner, 18X36 lagoon approx. 20,000 gallons odd shaped pool with different depths. 2 skimmers, 3 returns. Hayward 1HP pump, Hayward cartridge filter, Hayward chlorine feeder, Laars 250,000 BTU heater. Stenner pump with #2 tube for chlorine injection. Leslie branded Taylor test kit

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    Mod Squad jblizzle's Avatar
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    Re: Pool School CL and Heater recommended levels

    Here you go, HOCl as a function of CYA an FC levels:
    http://troublefreepool.com/~richardfalk/pool/HOCl.htm

    To have the equivalent HOCl as a FC of 2ppm in 0ppm CYA (0.967), for your 50ppm of CYA you would need to have a FC level of ~26ppm.
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    Re: Pool School CL and Heater recommended levels

    that's very interesting. So since HOCL is actually what kills algae, is it better to run at a higher FC level hence a higher HOCL? in my case of CYA of 50-60 my FC should be say 5-9 from Pool Math. There is significant difference between the HOCL numbers in fact looking at the chart I see number in blue and green do we want to keep it in the blue at all times? I am asking because the way I am running the stenner, I put the chlorine at after midnight to bring it up to 9, then I lose approx. 4PPM a day so I run it for 4 30 minute cycles(a 30 minute run adds 1PPM.) from reading this I should be at 9-10 PPM in the morning then add 1PPM every couple hours to maintain the 9-10 PPM. Or should it be even higher and then let it drop below 10 for PH and TA testing. I do follow the pool math numbers but I have algae sometimes on a couple walls where it may not be getting circulation as well. Also pool seems to pop more at higher numbers maybe letting it get down to the minimum every day should be avoided.

    Bottom line should we all be adding during the day to maintain the upper end of pool math for FC? To me that seems the case as there is more HOCL and I know that gives a better kill rate for organics.
    Location Charlotte NC. Pool is a IG vinyl liner, 18X36 lagoon approx. 20,000 gallons odd shaped pool with different depths. 2 skimmers, 3 returns. Hayward 1HP pump, Hayward cartridge filter, Hayward chlorine feeder, Laars 250,000 BTU heater. Stenner pump with #2 tube for chlorine injection. Leslie branded Taylor test kit

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    Re: Pool School CL and Heater recommended levels

    Most of the mathematics and charts from Chemgeeks work is here Pool Water Chemistry

    At the end of the first post is a link to his Pool Equations spreadsheet - which is awesome.

    As to the stenner/time question - to be honest it sounds like there is a little organic growth in the pool which is causing extra chlorine loss. It's probably worth slamming the pool to kill it all - and then maintaining a slightly higher FC level. In general I think it's easy to say more consistent chlorination throughout the day would be better - especially if you have a low circulation issue.
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    Mod Squad pooldv's Avatar
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    Re: Pool School CL and Heater recommended levels

    I avoid minimum like the plague. We have lots of inputs to our pool, lots of trees, squirrels, varmints, frogs, snakes, kids, birds, etc. I stay a couple above target and let target be my floor so I've got a little cushion. If you are seeing so easy algae you should brush that area more, SLAM now to kill it and keep FC a little higher after the SLAM
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    Re: Pool School CL and Heater recommended levels

    Since you seem to be bumping up against the higher than 10 ppm FC required CYA ratio and the over 10 ppm FC / Ph false reading issue, you might be better off to lower your CYA to 40 PM and keeping your FC below 10.
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