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Thread: Chlorine lock...is it real and what's the remedy?

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    Chlorine lock...is it real and what's the remedy?

    I have an 8 yr old, 25,000 gallon, chlorine pool. This summer for the first time we could not get the free chlorine level to register after adding large amounts of shock and turning the chlorinater on high. All other test readings stayed within the normal ranges and the water was clear. After speaking with different pool companies we got many different causes and solutions. Does anyone have any experience with this condition?

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    JoyfulNoise's Avatar
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    Re: Chlorine lock...is it real and what's the remedy?

    "Chlorine lock" is an old pool industry term for "anything we can't easily explain after selling this fellow all of our other magic potions for problems that did not exist". The next thing they're going to tell you is your water is "old and has gone bad."

    What they are referring to, and from what you have described, is that your pool water is over-stabilized. That is, the CYA (cyanuric acid or "stabilizer") is too high. All of that shock you dumped in the pool and all the cranking up of the chlorinator has added lots of CYA to your water. The chlorinator is full of 3" trichlor pucks, they contain CYA. The shock you used was likely dichlor, which also has CYA. So you've basically loaded up your water with CYA while trying to get the FC to register. The problem is that CYA in small amounts (less than 80ppm depending on pool type) is a blessing; CYA over 100ppm is a curse. If you read through enough posts here on TFP and through Pool School, you can learn the science and chemistry of CYA and it's relationship to FC.

    So the fix is this - you need to stop relying on pool companies and "pool experts" and take control of managing your own pool water. That starts with reading through Pool School and learning the ABC's of Water Chemistry. Next, you need to order your own test kits and learn to test your water yourself. The comparison of Test Kits is found HERE. You must then commit to The TFPC Method of pool care. And then you'll be totally free of the bad advice that is handed out at the pool stores which is designed solely to part you from your money.

    At the end of the day, your CYA level is probably off the charts high and so the only solution will be to drain some of your pool water and replace it with fresh fill water. How much that is and what you'll need to do can only be determined after we get reliable test results of your pool water. You can post Pool Store test results, but no one here will believe them. We typically only put stock in water testing that pool owners do themselves.
    Matt
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    Divin Dave's Avatar
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    Re: Chlorine lock...is it real and what's the remedy?

    ^^^ what Joyfulnoise said ^^^
    Divin Dave,
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    Re: Chlorine lock...is it real and what's the remedy?




    Is it real, yes it is just like Santa and the tooth fairy.
    It's just a way to shift blame away from whatever method is being used to maintain and sanitize a pool. IMHO it's usually pulled on unsuspecting pool store customers with high CYA levels from the stuff the pool stores have been selling them.
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    Mod Squad tim5055's Avatar
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    Re: Chlorine lock...is it real and what's the remedy?

    Matt has hit the nail on the head, 99.9% of the time what pool stores call chlorine lock is over stabilized water. You are in PA, so you are nearing the end of your pool season. Most probably you will be draining some amount of water to winterize your pool. This is what the pool stores count on, draining to reduce the stabilizer level. Unfortunately for you the level got too high before the end of the year.

    Knowledge will help solve the problem for you, start reading with Pool School - ABCs of Pool Water Chemistry

    This will give you an idea of your foe. Come back here and ask questions, we can point you in the right direction.

    There are other possibilities, and you may test with zero CYA, even after all the pucks and shock.

    But, you have to want to take control of the pool yourself. No more counting on the pool store to test water and sell you solutions. The first part of that control is your own accurate reliable test kit. I recommend the TF-100 at TFTestkits.net
    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: Chlorine lock...is it real and what's the remedy?

    "Chlorine Lock" sure sounds bad.

    The explainations given so far are correct, pool store makes thousands of dollars by selling customer (mark is a better term used by con artists) chemicals...water gets so full of those chemicals that nothing works...mark is told to drain and refill..mark comes back to spend thousands of dollars for chemicals...rinse and repeat.

    What a racket they have!
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    Re: Chlorine lock...is it real and what's the remedy?

    CYA doesn't prevent chlorine from showing up during testing.

    I'm more apt to believe that Bkmomof4 needs to add chlorine.

    First things first, please post full results from one of the approved test kits.
    18k gal AG Sand Filter K-2006

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    Swampwoman's Avatar
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    Re: Chlorine lock...is it real and what's the remedy?

    ^CYA doesn't stop it from showing up, but over-stabilization and nascent algae can certainly zero it out

    To the OP - what does your water look like right now? You said in your post it was "clear" but that you could not get chlorine to hold.

    There are some additional possible scenarios to entertain, but proper testing will be necessary to hazard any guesses.

    So your first step to get control of the pool is to purchase either a TFT100 or Taylor k2006 specifically since these are the only two kits that can read both CYA and high FC levels. Visit http://www.tfttestkits.net

    Once you have your own, reliable source of testing, please post your #s and we can help you figure out how to proceed.
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    Re: Chlorine lock...is it real and what's the remedy?

    Here's my 2....

    1. If it is true that you have no Free Chlorine, you are just before having serious algae problems. (Frankly, NO chlorine is unlikely and probably suggests testing errors.)

    2. As it seems clear that you have been visiting the pool store(s):
    .....We don't put any faith in the accuracy or the efficacy of pool store water testing. Buy one of the approved Taylor Reagent kits (EG. the K-2006C) and take charge of your pool.
    .....Unlike pool stores, we won't suggest that you use chlorine in powders or pills
    .....We don't shock our pool, nor do we need to.
    .....With regard to pool care: Total Dissolved Solids (TDS) is a meaningless term, Chlorine Lock is (as described in the pool store) a myth, you don't need algaecide, or anything else the pool store sells UNTIL...

    3. You use your own test kit for accurate results. Until you know where you ARE, there is little hope in you choosing the right direction towards success.

    4. Chemically, there is a phenomenon that mimics the false notion of "Chlorine Lock" that is caused by using powders and pucks, that are the stock in trade of the pool stores. Should you reach that point, replacing some or all of the water in your pool may be your only recourse.

    5. The bottom line is that we can't advise until we have good and reliable test numbers.

    PS
    As an afterthought, should your test numbers be in error, you may have FAR TOO MUCH chlorine in that pool to safely swim.

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    Re: Chlorine lock...is it real and what's the remedy?

    Quote Originally Posted by Bkmomof4 View Post
    I have an 8 yr old, 25,000 gallon, chlorine pool. This summer for the first time we could not get the free chlorine level to register after adding large amounts of shock and turning the chlorinater on high. All other test readings stayed within the normal ranges and the water was clear. After speaking with different pool companies we got many different causes and solutions. Does anyone have any experience with this condition?
    BKmomof4:

    Even though we do not trust pool store testing, can you please post a full set of results (CYA, CC, FC, CH, TA), to try and figure out exactly what the pool store is talking about. Chlorine Lock can be interpreted many different ways. In order for you to take control of your pool, it is highly recommended that you order one of the recommended test kits. Without this, you could always be second guessing yourself.

    It is very simple, if you are not registering FC (Free Chlorine), not TC (Total Chlorine), what this is suggesting is that all your chlorine from the 3" tablets in your chlorinator and the large amounts of shock that you are throwing in the pool is being consumed by "bad stuff", that simple. Please describe exactly what type of tablets you are using and what type of shock as well. How long have you been using these products. How often do you replace water, etc.

    Please add your signature. Thank you.

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    Re: Chlorine lock...is it real and what's the remedy?

    ^What he said^ ... and a carefully done CYA test wherever and however you can get one if you don't have a kit that will give you one. Generally the pool store isn't crooked, just sloppy!

    And if you can get results from two different stores, and order a Taylor test kit as recommended here.
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    Re: Chlorine lock...is it real and what's the remedy?

    Quote Originally Posted by Chuckiechan View Post
    ^What he said^ ... and a carefully done CYA test wherever and however you can get one if you don't have a kit that will give you one. Generally the pool store isn't crooked, just sloppy! And if you can get results from two different stores, and order a Taylor test kit as recommended here.
    Yes, that is correct. I sent a friend to 3 different pool stores that used the Taylor Test Kit, (same one), and the CYA level was off by at least 100 ppm (Wow!) and big differences in all 3 pool stores (at least to throw off your chemistry). One separate water bottle for a CYA dilution test and the pool store employee could not understand why the water was a 1:1 sample. They usually tell you your CYA is at 100, when in reality is sometimes double of that, if not higher. Most pool stores are sloppy, not crooked! They do not take their time, clean the vile, forget how many drops they put in, and the list goes on. The bad pool stores are the ones that use "Test Strips" for their testing.

    My friend then ordered a TF-100 test kit as she understood finally, after 10 years that she can no longer keep the same routine up! It is not the first friend that purchased a quality test kit after finally understanding.
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