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Thread: Added shock chlorine but sill, FC = 0 ?

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    Added shock chlorine but sill, FC = 0 ?

    I opened my 4500 gal above ground pool and added a gallon of 12% liquid chlorine. After circulating a while, the test strips show no free chlorine. So, i added a second gallon. Same result. I've never seen this. Usually one gallon is fine to start the summer. Any ideas? is the chlorine bad or is it being immediately used up? We had a bad rain storm the night before and there was a lot of organic material in the pool from overhead trees. I cleaned it out before adding the chlorine.

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    Mod Squad YippeeSkippy's Avatar
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    Re: Added shock chlorine but sill, FC = 0 ?

    Welcome Chiss, is the 12% liquid chlorine new? Can you read the date stamp on it- it should be a Julian date like 2016134 (2016, 134th day of the year)

    How does your water look? Cloudy, clear? Green?

    We don't trust "Guess-Stips" and always suggest you have one of the tests we do trust. The FAS-DPD portion of those test kits is the *most* important element as it will read FC up to 50 ppm. This website is the source: TFTestkits.net

    I would also suggest that you start reading this link in Pool School- ABCs of Pool Water Chemistry as well as other Pool School articles to get you up to speed.
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    Richard320's Avatar
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    Re: Added shock chlorine but sill, FC = 0 ?

    Welcome!

    If the chlorine is really high, the test strip can bleach out and read falsely low.

    If there's no CYA in the water, sunlight will destroy all the FC in a couple hours.

    If there's algae or organic material in the water, it will consume the bleach almost as fast as you can pour it in.

    Liquid Chlorine has a finite shelf life. If the stuff you have has been sitting since last season, it could be little more than bleach-scented salt water.

    So... If you have a green pool with no CYA and some old bleach, it could all disappear in a big hurry. Or it could be so strong it just bleached out the strip. That's why even for little kiddie pools that can be easily dumped out if there's a problem, we recommend a drop-type test.
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    Re: Added shock chlorine but sill, FC = 0 ?

    Thanks for the quick replies! The chlorine (purchased yesterday) is dated 9/5/2015. Is this outdated? I noticed it does not have a strong bleachy smell as i would think.

    The water was light green but is now cleared after running the filter and vacuuming. There is still quite a bit of stuff from the nearby trees falling in during the day. I am skimming it out periodically.

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    Richard320's Avatar
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    Re: Added shock chlorine but sill, FC = 0 ?

    Yeah, that bleach is just expensive salt water by now. Probably sat outside the last six months.

    As if you didn't have enough clouding your brain... Breakdown of bleach over time by storage temperature
    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: Added shock chlorine but sill, FC = 0 ?

    Thanks. That would explain why it was on sale! I have some powdered shock left over from last year (at least). does this also go bad over time?

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    Re: Added shock chlorine but sill, FC = 0 ?

    Quote Originally Posted by chliss View Post
    Thanks. That would explain why it was on sale! I have some powdered shock left over from last year (at least). does this also go bad over time?
    If it stays dry, it's good for years. However... Dichlor and Trichlor are both acidic and raise CYA. Cal-hypo adds Calcium. Do you want or need those side effects? Pool School - How to Chlorinate Your Pool
    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: Added shock chlorine but sill, FC = 0 ?

    Thanks for all your help. This forum is very informative and prompt

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    Re: Added shock chlorine but sill, FC = 0 ?

    A follow up:I took water to the pool store for testing. It showed very high total chlorine and almost no free chlorine. Does this make sense? What should i do to bring it to the right level and ratio? The pool is still clear

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    Re: Added shock chlorine but sill, FC = 0 ?

    It can happen. That means the algae (or whatever organics) in the pool are being consumed by FC which creates CC. Keep slamming.
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    Re: Added shock chlorine but sill, FC = 0 ?

    Quote Originally Posted by chliss View Post
    A follow up:I took water to the pool store for testing. It showed very high total chlorine and almost no free chlorine. Does this make sense? What should i do to bring it to the right level and ratio? The pool is still clear
    Chlorine is an oxidizer. So is fire. So consider bleach to be sort of flameless combustion. CC is sort of halfway oxidized stuff, the smoke and soot and charred bits of the pool world. How do you get a fire to stop smoking and burn up all those bits of charcoal? Turn up the heat!

    So the answer to eliminating CC is

    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: Added shock chlorine but sill, FC = 0 ?

    so, i should add stabilizer and more liquid chlorine ?

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    Re: Added shock chlorine but sill, FC = 0 ?

    Quote Originally Posted by chliss View Post
    so, i should add stabilizer and more liquid chlorine ?
    What is the CYA level? And is it your test or the pool store's?
    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: Added shock chlorine but sill, FC = 0 ?

    CYA was very low as tested at the store and they recommended stabilizer. My home test strip shows less than 30 but more than 0. (I have a real test kit on order)

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    Re: Added shock chlorine but sill, FC = 0 ?

    According to poolmath, one 8 oz trichlor puck will add 12 FC and 7.4 CYA to your 4500 gallon pool. It will also lower pH some. Poolmath says by .65, but that is only an estimate and doesn't take TA levels into account. So you probably have room for two. A one pound package of dichlor will be 15 FC and 13 CYA and about the same pH drop. You don't want CYA to get above 30 while doing a SLAM, which is sort of what you're trying, although without the FAS-DPD tester you can't.

    Your pool is so small, why not just dump it and scrub it out and start fresh? The water will probably only cost you a few bucks. Check your rates. See how much 6 CCF will cost you.
    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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