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Thread: HOw much will rain effect chlorine level?

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    HOw much will rain effect chlorine level?

    I have a SWG- usually run it for 12 hours at 55-60% and it maintains chlorine between 3-5
    Lately I've been increasing it almost every day by 5%. UP to 85% now and still at 1-3 on chlorine.
    It's been raining a lot lately- I get that there is no chlorine in rain and it will dilute the pool water, but this seems excessive...
    My other guess is that I got the CYA up a little too high?

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    Mod Squad YippeeSkippy's Avatar
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    Re: HOw much will rain effect chlorine level?

    Are you sure nothings growing in the pool somewhere and eating your chlorine up?

    How does your water look?
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    Re: HOw much will rain effect chlorine level?

    The effect rain has on swimming pools is an urban myth that I hope we get disspelled some day.

    It has virtually no effect.
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    poolnoob.ca's Avatar
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    Re: HOw much will rain effect chlorine level?

    The cl/cya chart suggests 4-6 ppm Cl with 80 cya, so maybe a quick slam will get you back on track? An OCLT might be in order? as you said maybe drain and fill a bit to get down to 70 CYA?
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    Re: HOw much will rain effect chlorine level?

    I'd try to do an OCLT to see what's going on.
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    Re: HOw much will rain effect chlorine level?

    With a CYA level of 80 and the FC down to 3 is a recipe for a SWG pool to develop nascent algae. You need to follow the Chlorine CYA Chart to avoid algae.

    Like the others have already said, run an OCLT with an elevated chlorine level, I like to shoot for 10ppm for a first test. Make sure the SWG is off during the test.
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    Re: HOw much will rain effect chlorine level?

    Thanks.
    Will run the test tonight.
    I still have a hard time getting my head around the CYA...
    If CYA is where it should be, does it require more chlorine to get it at recommended levels, but once it's there it takes longer to go back down?
    By looking at the charts, it seems that the higher the CYA, the more chlorine you need to add. But once you got it where it needs to be, is it more 'resistant' to the sun bringing it back down?
    Maybe I just need to boost the chlorine with a little bleach to get the levels up a bit?
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    poolnoob.ca's Avatar
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    Re: HOw much will rain effect chlorine level?

    Hi jim, in doing the oclt test at 10ppm You will need liquid chlorine or bleach to get it that high anyway

    P.s. Yes higher cya does require higher fc levels, and it does protect the chlorine from uv breakdown
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    Re: HOw much will rain effect chlorine level?

    Quote Originally Posted by duraleigh View Post
    The effect rain has on swimming pools is an urban myth that I hope we get disspelled some day.

    It has virtually no effect.
    X 100 virtually none
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    Re: HOw much will rain effect chlorine level?

    based on FC of 2 with your CYA level, you probably have an algae outbreak. also, SWCG are great at keeping your FC levels consistent, but not good at trying to keep up with algae growth. they just don't produce enough chlorine, especially if the cell isn't way oversized.

    You need to do the OCLT test, if you fail that, you need to SLAM. once you SLAM, and let your FC fall back to the correct level, you then set your SWCG to maintain the FC level. turn off your SWCG while SLAMing

    and to answer original question about the rain. well it has the same exact affect as when you top off your pool with tap water. NONE. other than a small percentage reduction due to dilution. example i use is a pool with average depth of 4 feet, if you get 2 inches of rain, that's a 4% increase in volume, so your FC (and all levels) go down by 4%.. but once that evaporates off, its back to the same exact number.
    Dan
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    Re: HOw much will rain effect chlorine level?

    thanks all
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    Re: HOw much will rain effect chlorine level?

    Quote Originally Posted by DaninFLA View Post
    based on FC of 2 with your CYA level, you probably have an algae outbreak. also, SWCG are great at keeping your FC levels consistent, but not good at trying to keep up with algae growth. they just don't produce enough chlorine, especially if the cell isn't way oversized.
    Would you suggest "supplementing" in bleach here and there to keep the levels higher?
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    Re: HOw much will rain effect chlorine level?

    Quote Originally Posted by Jim H View Post
    Would you suggest "supplementing" in bleach here and there to keep the levels higher?
    I don't. once you get your pool SLAMed, you don't have algae. its very easy to dial in the SWCG to keep a steady FC. only time I added liquid bleach is after having a lot of people in the pool. i bump it up, and SWCG keeps it there.
    Dan
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    Re: HOw much will rain effect chlorine level?

    Exactly! I raised my CYA to 50 and although my FC levels have to be higher, I'm losing less during a 24 hour period thus having to add less bleach daily.


    Quote Originally Posted by Jim H View Post
    Thanks.
    Will run the test tonight.
    I still have a hard time getting my head around the CYA...
    If CYA is where it should be, does it require more chlorine to get it at recommended levels, but once it's there it takes longer to go back down?
    By looking at the charts, it seems that the higher the CYA, the more chlorine you need to add. But once you got it where it needs to be, is it more 'resistant' to the sun bringing it back down?
    Maybe I just need to boost the chlorine with a little bleach to get the levels up a bit?
    Cornelius Monterey Steel/Resin AG 18' round (approx. 7600+gallons) Hayward veri-flo SWG w/sand filter.Testing w/ TK2006 using Speed stir.

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    Re: HOw much will rain effect chlorine level?

    Quote Originally Posted by Patrick_B View Post
    X 100 virtually none
    Try having a SWG pool located in the rainiest (by volume) city in the country Rain water will absolutely dilute the salt content.
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    Re: HOw much will rain effect chlorine level?

    Quote Originally Posted by Roy Hobbs View Post
    Try having a SWG pool located in the rainiest (by volume) city in the country Rain water will absolutely dilute the salt content.
    dilution is different than what the myth that people believe that rain consumes up your chlorine. obviously if you are losing water to overflow and refilling with rain water you are going to dilute concentrations of everything.
    Dan
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