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Thread: Question about chlorine lock

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    Re: Chlorine Lock Causes?

    I am also having an issue with chlorine. Last year we could not keep the chlorine level high enough to show up on a test. The CYA levels were fine. This year we drained some of the water but still cannot get a chlorine reading to last more than a couple hours. What do you suggest?

    Finally got my test kit. Result from yesterday are:
    CYA 80
    FC 7 (after adding 2gal bleach)
    CC 2.5
    ph 7.5
    TA 180
    CH 400

    This morning the readings were:
    FC .5
    CC 2

    The water is crystal clear and there is no algae. Do we need to keep the chlorine level at 6 as stated in the chart for it to be safe to swim in?

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    Richard320's Avatar
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    Re: Question about chlorine lock

    Something's eating your chlorine. It's either organics or sunlight.

    Organics include things like leaves and twigs, algae, and the A-word: Ammonia.

    A seriously green pool will devour chlorine like nobody's business, but you ought to be showing something on the test if you checked it within an hour of adding chlorine. A pool with Ammonia makes a green pool look anorexic. It'll eliminate chlorine as fast as you can pour it in the water.

    The place to start is with some test results. Also, tell us where they came from (what kit) and what kind of pool and equipment you have, and what the water looks like.
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    Mod Squad jblizzle's Avatar
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    Re: Question about chlorine lock

    Welcome Back! I moved this question into its own thread.

    I suggest you read all 11 of the responses in the thread you started last year and then see if you still have questions:
    Chlorine lock...is it real and what's the remedy?
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    Re: Question about chlorine lock

    It is probably ammonia take a look at THIS thread. Also what kind of test kit do you have others will be along shortly and it will be helpful if you can post some test results.
    12,300 Gallon, IG PebbleFina, 3 ft sheer, 2 Jandy nicheless LED lights, Jandy Pro 1.5HP VS pump (A.O. Smith Motor), PB4-60 Booster pump, Polaris 280, Jandy cv340 cartridge filter, Zodiac Z4 control panel W/iAquaLink, Stenner pumps for chlorine & MA connected to WiOn WiFi switches, TF-100. You can support TFP with AmazonSmile just click the link!

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    Re: Question about chlorine lock

    bkmomof4,

    Welcome to the forum.

    As you continue to read, you will find that we teach that you take the bull by the horns and learn to manage your pool. In short, "Stay out of the Pool Store"

    Anyone talking with you about chlorine lock is either terribly under educated or simply doesn't want to learn.

    Chlorine Lock is a myth that doesn't exist. If you decide to learn what we teach here at TFP, we will promise you will end up with crystal clear water and a whole new understanding of how this all works

    You will find it increasingly difficult to follow our advice and then follow pool store advice as well. The two simply don't mix well.
    Dave S.
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    Re: Question about chlorine lock

    Welcome to TFP Bkmomof4

    Chlorine lock should end up on myth busters so it can be debunked. IMHO, It's something the pool store person will say when they don't know what's going on. Usually followed by a 30 to 60 bottle of "try this".

    A photo of the water would be helpful as would adding your pools and equipment information in your signature as outlined here: Pool School - Getting Started

    The more information we have the more accurate and helpful the response

    As stated above it's more likely something is eating your chlorine. Need to know your CYA level and what you are using for a chlorinator and if it's your test results or you are having the pool store test for you.

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    Re: Chlorine Lock Causes?

    Finally got my test kit in the mail. Results from yesterday are:
    CYA 80
    FC 7 (after adding 2gals bleach)
    CC 2.5
    ph 7.5
    CH 400
    TA 180

    This morning results were
    CC .5
    CC 2

    the water is crystal clear and no algae. Do I need to keep the chlorine level at 6 as stated on the chart in order for the water to be safe for swimming?
    25K, IG vinyl, sand filter, 10 yrs old, TF100 test kit, elec htr

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    Re: Question about chlorine lock

    Check your math... CC of .5 and CC of 2 at the same time? I think you mean FC of 2 and CC of .5. If you had an FC of 7 last night and FC of 2 today, you have something organic growing in your pool. Was your initial FC of 7 taken near dusk, or earlier in the day?
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    Re: Question about chlorine lock

    Quote Originally Posted by RobbieH View Post
    Check your math... CC of .5 and CC of 2 at the same time? I think you mean FC of 2 and CC of .5. If you had an FC of 7 last night and FC of 2 today, you have something organic growing in your pool. Was your initial FC of 7 taken near dusk, or earlier in the day?
    Agreed. Just because water is clear doesn't mean something isn't growing in it sight unseen. I had clear water last year after an oops on my part that was consuming 3ppm FC overnight...
    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: Question about chlorine lock

    The initial test was taken around 5pm. The morning results were as written
    FC .5
    CC 2
    25K, IG vinyl, sand filter, 10 yrs old, TF100 test kit, elec htr

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    Re: Question about chlorine lock

    OK, that's a clear indication that you have algae. Time to SLAM:

    Pool School - SLAM - Shock Level And Maintain
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    Re: Question about chlorine lock

    Per the chart I'd need to reach a 31 chlorine level to slam. My CYA is 80. Probably not realistic. There is no visible algae growth. Is it safe to swim in?
    25K, IG vinyl, sand filter, 10 yrs old, TF100 test kit, elec htr

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    Re: Question about chlorine lock

    Quote Originally Posted by Bkmomof4 View Post
    Per the chart I'd need to reach a 31 chlorine level to slam. My CYA is 80. Probably not realistic. There is no visible algae growth. Is it safe to swim in?
    Do you mean it is not realistic to fix the issue?

    Personally, I will not swim in a pool that will not hold FC, or one that has algae.
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    Mod Squad jblizzle's Avatar
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    Re: Question about chlorine lock

    Why is that not realistic? That is exactly what you need to do until you pass the 3 criteria to stop. You are currently only passing 1 of them.
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    Re: Question about chlorine lock

    You have nascent algae. There is just enough chlorine being added to keep the algae from blooming, but not enough chlorine to kill off all the algae.

    Believe me, you need to complete the SLAM process or you will go through 10 times more chlorine than you should. Been there done that.
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    Re: Question about chlorine lock

    Quote Originally Posted by ping View Post
    You have nascent algae. There is just enough chlorine being added to keep the algae from blooming, but not enough chlorine to kill off all the algae.

    Believe me, you need to complete the SLAM process or you will go through 10 times more chlorine than you should. Been there done that.
    We all have learned this the hard way at least once I think.
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    Richard320's Avatar
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    Re: Question about chlorine lock

    Quote Originally Posted by Bkmomof4 View Post
    Per the chart I'd need to reach a 31 chlorine level to slam. My CYA is 80. Probably not realistic. There is no visible algae growth. Is it safe to swim in?
    Just a thought... have you added any non-chlorine "shock"? That's stuff like Chlor-free and Oxone. MPS will give a false high CC reading.

    If the pH is in range and the FC is above minimum for the CYA level, then technically I guess the pool is safe to swim in. People have been swimming in rivers and lakes and ponds with no test results for centuries and haven't been dying from it. But if that CC is CC and not interference, expect skin irritation and burning eyes.

    Taking FC up to 31 is not so difficult. It's just a matter of emptying some jugs. If you get a good kill on whatever is growing -- and it can't be much if the water is clear -- then maintaining it shouldn't take any huge volume of bleach. It's just getting it up there initially that looks so daunting. And if it does have an unquenchable thirst for bleach, then it's just a matter of time before the pool turns to a swamp.

    Also check for algae lurking behind lights and stairs and inside ladders. You still haven't filled out your signature so we have no clue what we're dealing with.
    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: Question about chlorine lock

    Thanks Richard 320. What else would you like to know that is not in my signature?
    25K, IG vinyl, sand filter, 10 yrs old, TF100 test kit, elec htr

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    Re: Question about chlorine lock

    I have been slamming since Tuesday. This morning(Saturday) my FC had a 2.5 loss overnight and the CC was 1.5. I followed the prep instructions to the letter. I have added at least 40 gallons of bleach. Am I doing something wrong? This seems extreme considering the water looked good before I started.
    25K, IG vinyl, sand filter, 10 yrs old, TF100 test kit, elec htr

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