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Thread: CYA reduction arithmetic; CYA decay?

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    Post CYA reduction arithmetic; CYA decay?

    What an excellent site!

    It's been obvious to me for a while that my CYA is way too high, through using dichlor for ages. Only through reading this site did I find that out. I just ordered a kit with a CYA test, but already I'm sure: adding yet more dichlor or even hypo barely registers chlorine on the Cl test, and the algae won't die! No problem with pH: very close to 7.2 with small monthly doses of carbonate. So, two suggestions/questions (for comment please).

    1) Reducing the CYA (don't know the level yet, probably way over 100)... I doubt draining is possible for most vinyl pools, so I did the step-wise arithmetic for my pool, 16 x 32 rectangular. Pumping out a manageable 15 inches comes to about 5K gal. After draining, refill to skimmer. Repeating this three times--at the cost of 15K gal of fresh water--will reduce the concn of dissolved stuff by about 55%. Possibly more if you pump only from the drain and point the refill hose to the surface. When I do it and have the CYA numbers I'll let you know how it goes.

    2) What's the consensus on optimum CYA for reasonable Cl buffering: around 30, or less?

    3) Assuming I use mostly sodium hypochlorite (bleach) to shock and chlorinate after reducing the CYA, what acid should I use to neutralize that: dry bisulfate or muriatic (sulfuric)?

    4) Does CYA ever go away/degrade, or am I stuck with it? (Of course every time I backwash some water goes out the drain, and more is lost on closing and reopening the pool. All of that is replaced by rain or from the hose, probably about 5K gal per year.)

    5) I'm probably missing something else important...please inform!

    Many thanks

    JJ
    Long Island NY. Old 16x32 vinyl, basic IG pool. 3 ft shallow, 8 ft deep end. Ca. 22K gal. 1 hp Hayward pump, Triton II T60 sand filter.

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    Smykowski's Avatar
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    Re: CYA reduction arithmetic; CYA decay?

    Welcome to the forum!

    Answers in red below....

    Quote Originally Posted by Jo Jesty View Post
    What an excellent site!

    It's been obvious to me for a while that my CYA is way too high, through using dichlor for ages. Only through reading this site did I find that out. I just ordered a kit with a CYA test, but already I'm sure: adding yet more dichlor or even hypo barely registers chlorine on the Cl test, and the algae won't die! No problem with pH: very close to 7.2 with small monthly doses of carbonate. So, two suggestions/questions (for comment please).

    1) Reducing the CYA (don't know the level yet, probably way over 100)... I doubt draining is possible for most vinyl pools, so I did the step-wise arithmetic for my pool, 16 x 32 rectangular. Pumping out a manageable 15 inches comes to about 5K gal. After draining, refill to skimmer. Repeating this three times--at the cost of 15K gal of fresh water--will reduce the concn of dissolved stuff by about 55%. Possibly more if you pump only from the drain and point the refill hose to the surface. When I do it and have the CYA numbers I'll let you know how it goes. Remember that CYA is only a part of total dissolved solids.

    2) What's the consensus on optimum CYA for reasonable Cl buffering: around 30, or less? 30-50 for manually chlorinated pools.

    3) Assuming I use mostly sodium hypochlorite (bleach) to shock and chlorinate after reducing the CYA, what acid should I use to neutralize that: dry bisulfate or muriatic (sulfuric)? Adding bleach is a net pH neutral event.

    4) Does CYA ever go away/degrade, or am I stuck with it? (Of course every time I backwash some water goes out the drain, and more is lost on closing and reopening the pool. All of that is replaced by rain or from the hose, probably about 5K gal per year.) No, CYA only leaves the pool when water (with CYA in it) goes overboard, usually in the methods you referenced.

    5) I'm probably missing something else important...please inform!

    Many thanks

    JJ
    33' round, 23,000 gal AG vinyl , 1HP 2spd PowerFlo Matrix downsized with 3/4HP impeller (X2), Hayward S180T 150# sand filter (X2), Hayward H250 NG heater Pool Store year 1 - $850 for 2 months; Pool Store year 2 - $440 for 2 months, TFPC year 1 - $170 for 4 months; TFPC year 2 - $95 for 4.5 months
    The most important article on this site - The ABCs of Pool Water Chemistry

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    Mod Squad jblizzle's Avatar
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    Re: CYA reduction arithmetic; CYA decay?

    Welcome to TFP!!!

    Just to add to the above answer for #4: The CYA does degrade, but very slowly. Like 3-5ppm per month. There are also times over the winter when a bacteria will convert the CYA often to ammonia which requires a lot of chlorine to get rid of, but the CYA will be gone.

    Does sound like you need to replace water and get the CYA down. You should leave at least a foot of water in the shallow end.
    Then you will need to follow the ShockLevelAndMAINTAIN Process to clear up the pool.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
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    Re: CYA reduction arithmetic; CYA decay?

    Thank you SO much. I will follow up when I've gone thru the partial draining and shock etc. BTW, with regular brushing (green matter on the floor sucked down the drain into the filter) and vacuuming (old little Arneson, super gadget), the pool is just slightly cloudy, perfectly swimmable. But it's near-daily work to keep it that way when the water is much over 80F. JJ
    Long Island NY. Old 16x32 vinyl, basic IG pool. 3 ft shallow, 8 ft deep end. Ca. 22K gal. 1 hp Hayward pump, Triton II T60 sand filter.

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    Re: CYA reduction arithmetic; CYA decay?

    1. leaving a foot in the shallow end of my vinyl pool 5 times to get my cya from over 350 to 50 was entirely possible. Just do a diluted sample to find out how many times depending on your results you may have to perform the process.
    Pool size: 24000gal inground Vinyl-Taylor k-2006 and k-1766 test kits and-speed stir
    Intermatic P1353ME digital timer w/freeze sensor
    CircuPool Si-45 SWCG System
    Polaris 280 vacuum/Polaris PB4-60 boost pump
    Pentair IntelliFlo VS 3hp Pump--Pentair sand filter

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    Mod Squad jblizzle's Avatar
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    Re: CYA reduction arithmetic; CYA decay?

    If you properly maintain adequate FC levels (function of your CYA), then there will not be any green to keep scrubbing daily.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
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    Re: CYA reduction arithmetic; CYA decay?

    If you decide to replace some water it is better to fill in with a hose close to the deep end of the pool and discard the excess water from a skimmer. Usually the fresh weater is colder and will say at the bottom of the pool while the last year water is warmer and will stay closer to the surface. The new and the old water will not mix if you do not tun the pool pump with the filtation system. In this way you discard only the water containing high concentration of cya.

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    Re: CYA reduction arithmetic; CYA decay?

    All turned out well, thanks to the excellent advice. By Taylor's kit, CYA was about 130! Pumping out about 15K gal, I got it down to about 40 (reading that black dot depends a lot on lighting!). I pumped down to about 1 ft, like TimerGuy, and added gently into the shallow end from the hose. Now I can easily get a reasonable FC, 1-2 ppm, using 12% hypochlorite ($25 for 4 gal case at the pool store, not bad), 2-3 cups a day. If I dopn't use the pool, I still have algae a bit at the end of the week--I'm sure when I vacuum half of it just goes straight thru the filter and back in the pool--and I'm thinking of replacing my sand with glass, which seems to be the best-recommended alternative for actually catching algae (like my old, defunct, DE filter used to do so well). And Smykowski was right about the pH: on adding a shock, it rises; but then it settles back down again as the hypochlorite makes chlorine. Thanks again.
    Long Island NY. Old 16x32 vinyl, basic IG pool. 3 ft shallow, 8 ft deep end. Ca. 22K gal. 1 hp Hayward pump, Triton II T60 sand filter.

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    Mod Squad tim5055's Avatar
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    Re: CYA reduction arithmetic; CYA decay?

    If you still have algae in the pool a SLAM is in order. Once you eradicate all of it as long as you keep the FC above the minimum for your CYA level it should not return.

    Sand replacement is very seldom necessary. It is possible you have channeling in your sand filter and need to do a deep cleaning of the sand to fix it.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: CYA reduction arithmetic; CYA decay?

    Correct me if I'm wrong, but I don't think I've seen how (what test kit?)You're using to test your pool. If you don't have one, you really need to get an adequate test kit such as the TF-100 or Taylor k-2006-- both of which can be ordered at TFkits.net.
    Whoops I just found you used a Taylor for your cya. I hope it's the k-2006 so you have a fas-dpd chlorine test.
    Pool size: 24000gal inground Vinyl-Taylor k-2006 and k-1766 test kits and-speed stir
    Intermatic P1353ME digital timer w/freeze sensor
    CircuPool Si-45 SWCG System
    Polaris 280 vacuum/Polaris PB4-60 boost pump
    Pentair IntelliFlo VS 3hp Pump--Pentair sand filter

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    Mod Squad jblizzle's Avatar
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    Re: CYA reduction arithmetic; CYA decay?

    A FC of 1-2ppm is way too low for a cya of 40ppm. That is why you see algae and now need to follow the SLAM process.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

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