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Thread: My chlorine readings drop like a brick

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    My chlorine readings drop like a brick

    I actually have a related question to FCL and CYA levels. My chlorine readings drop like a brick in just a day or two. Ph and Alkalinity and other levels are within range. My CYA reading is only 26ppm. Should I significantly bump it up? Any downsides to a high CYA level? I always thought 20-40ppm was a good range? Maybe I'm wrong? Also the plaster is about 30 days old if that were to make a big difference. The pool gets a lot of sunlight as well (which would break down chlorine, correct?)

    Thanks!!

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    Mod Squad zea3's Avatar
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    Re: Colder water and it's impact on chlorine

    Quote Originally Posted by NoPool4U
    I actually have a related question to FCL and CYA levels. My chlorine readings drop like a brick in just a day or two. Ph and Alkalinity and other levels are within range. My CYA reading is only 26ppm. Should I significantly bump it up? Any downsides to a high CYA level? I always thought 20-40ppm was a good range? Maybe I'm wrong? Also the plaster is about 30 days old if that were to make a big difference. The pool gets a lot of sunlight as well (which would break down chlorine, correct?)

    Thanks!!
    Hi! I have asked the mods to move your question to a new thread so the answer for you doesn't confuse someone who is looking for information related to the original post in this thread.

    As for your question, how high your CYA should be depends on whether or not you are using a SWG for your chlorine, and what part of the country your pool is in. If you are in a desert climate you can get away with a higher level of CYA than most other parts of the country. For an average pool the CYA should be between 30-50ppm. Anything lower will not protect the chlorine well and it will burn off quickly. Levels significantly higher than 50 protect the chlorine too well, so that the chlorine is unable to work efficiently and more chlorine is required to "overwhelm" the protective properties of the CYA in order to sanitize the pool.

    If you are using a SWG as your source of chlorine then you want the CYA to be between 60-70ppm. This works because the SWG generates chlorine at a consistent rate over a longer period of time.

    If you are manually chlorinating your pool you may want to bump it up about 10ppm to keep it in the 30-50ppm range. Yes sunlight will break down chlorine quickly without some CYA protection. Just don't over do it!

    If you don't mind giving us a little more information, such as your climate, how you chlorinate and with what and how you test your water we may be able to fine tune the answer a little closer to your situation.
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    Re: Colder water and it's impact on chlorine

    Thanks for the quick info!

    I'm in Southern CA, so the climate is pretty dry with a temp between 60 and 80F pretty much year round. I use liquid chlorine to chlorinate the water. I read my levels with the latest version of the ColorQ.

    It sounds like I should definitely bump up the CYA level to at least 30-40ppm.

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    dmanb2b's Avatar
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    Re: My chlorine readings drop like a brick

    NoPool4u...I moved your question into it's own thread. Please do not threadjack. Thanks
    24'x52" AGP (13,500 Gallons), Intex SWG, (2)Solar Bear 4x20 panels, Hayward S220T Filter, 1/2hp Pentair Superflo

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    Re: My chlorine readings drop like a brick

    Quote Originally Posted by NoPool4U
    I actually have a related question to FCL and CYA levels. My chlorine readings drop like a brick in just a day or two. Ph and Alkalinity and other levels are within range. My CYA reading is only 26ppm. Should I significantly bump it up? Any downsides to a high CYA level? I always thought 20-40ppm was a good range? Maybe I'm wrong? Also the plaster is about 30 days old if that were to make a big difference. The pool gets a lot of sunlight as well (which would break down chlorine, correct?)

    Thanks!!
    Off to Pool School with you!

    You need more CYA since you get a lot of sun. Shoot for 40-50. If Pool Calculator says 18 oz is needed and it comes 16 oz to a package, use 16. Get it?

    The downsides to high CYA are:

    That you can't use a color block to read your FC, has to be FAS-DPD every time, since the block stops at 5.

    If by chance you do get an algae bloom, shock level is astronomical, which pretty much means you'll have to do a partial drain, which we don't like to do here in SoCal during water restrictions.

    If you overdo it, the only way to remove it is by draining.[/list]
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: My chlorine readings drop like a brick

    Thanks again for the info! I'm definitely increasing my CYA level and will see how much improvement I get. Currently all levels are good

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    Re: My chlorine readings drop like a brick

    Just to give an update on this. I raised the CYA level to about 40 and started using the chlorine tablets again and the levels remain very steady now. I don't even have to add liquid chlorine; the tablets seem to be sufficient.

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    Richard320's Avatar
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    Re: My chlorine readings drop like a brick

    Quote Originally Posted by NoPool4U
    Just to give an update on this. I raised the CYA level to about 40 and started using the chlorine tablets again and the levels remain very steady now. I don't even have to add liquid chlorine; the tablets seem to be sufficient.
    Careful....

    You may be overdoing the CYA or adding to your almost-certainly-high CH. Be sure to keep testing all the parameters. 5FC with CYA 150 is no good.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: My chlorine readings drop like a brick

    Quote Originally Posted by Richard320
    Quote Originally Posted by NoPool4U
    Just to give an update on this. I raised the CYA level to about 40 and started using the chlorine tablets again and the levels remain very steady now. I don't even have to add liquid chlorine; the tablets seem to be sufficient.
    Careful....

    You may be overdoing the CYA or adding to your almost-certainly-high CH. Be sure to keep testing all the parameters. 5FC with CYA 150 is no good.
    Oh, definitely! FCL and TCL are both about 3ppm. CYA seems to remain pretty steady around 40.

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    Richard320's Avatar
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    Re: My chlorine readings drop like a brick

    Quote Originally Posted by NoPool4U
    Quote Originally Posted by Richard320
    Quote Originally Posted by NoPool4U
    Just to give an update on this. I raised the CYA level to about 40 and started using the chlorine tablets again and the levels remain very steady now. I don't even have to add liquid chlorine; the tablets seem to be sufficient.
    Careful....

    You may be overdoing the CYA or adding to your almost-certainly-high CH. Be sure to keep testing all the parameters. 5FC with CYA 150 is no good.
    Oh, definitely! FCL and TCL are both about 3ppm. CYA seems to remain pretty steady around 40.
    What is CH? And what kind of pucks are you using in the floater? You're adding CYA or CH by using pucks - there is no form of solid chlorine without something else. It's one or the other. If CYA is steady, then CH must be climbing. And you can't get rid of excess calcium or cyanuric acid easily. So it's better not to add too much.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: My chlorine readings drop like a brick

    Quote Originally Posted by Richard320
    What is CH? And what kind of pucks are you using in the floater? You're adding CYA or CH by using pucks - there is no form of solid chlorine without something else. It's one or the other. If CYA is steady, then CH must be climbing. And you can't get rid of excess calcium or cyanuric acid easily. So it's better not to add too much.
    Now it all makes sense. The CYA level did go up by a few points, so I was wondering if my reading was off, so it must be the chlorine tablets! I'll stop using the tablets and revert back to liquid chlorine. CYA is now in the 40s, which is still acceptable for here I assume? CH is about 400ish; a little high but I guess it might drop a bit with the rainfall.

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