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Thread: Is Chlorine block a real thing?

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    Is Chlorine block a real thing?

    We have a 15x20 above ground pool. Been using BBB method (this is 3rd year). Got a new liner this year, so started with brand new water in May. CANNOT keep chlorine in pool. pH is right at 7.4 almost always. TA = 110. CYA = 40. I put an entire jug of chlorine (8.5% Clorox) in last night because it was looking cloudy. Today? Zero reading. Most days it reads .5 or 1.0 max. What's the deal?

    Apologize for anything in my signature- on my mobile and it won't let me view or edit it, and I haven't posted in quite awhile. Thanks in advance for any ideas.

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    AimeeH's Avatar
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    Re: Is Chlorine block a real thing?

    Welcome (back) to TFP

    In a word.....no. Chlorine block/lock is not a real thing.

    If the water is cloudy and you add bleach it likely was consumed by algae that made the water cloudy. Can you share more detail like gallons of pool and how you are testing?
    18*36*23 true "L" vinyl IG 29,000 gallons. SWG. TF-100 test kit.
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    Mod Squad pooldv's Avatar
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    Re: Is Chlorine block a real thing?

    Perform the Overnight Chlorine Loss Test to see if there is algae. If it fails then SLAM to kill the algae that is consuming all of your chlorine.
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    Re: Is Chlorine block a real thing?

    Quote Originally Posted by Guppy1013 View Post
    We have a 15x20 above ground pool. Been using BBB method (this is 3rd year). Got a new liner this year, so started with brand new water in May. CANNOT keep chlorine in pool. pH is right at 7.4 almost always. TA = 110. CYA = 40. I put an entire jug of chlorine (8.5% Clorox) in last night because it was looking cloudy. Today? Zero reading. Most days it reads .5 or 1.0 max. What's the deal?

    Apologize for anything in my signature- on my mobile and it won't let me view or edit it, and I haven't posted in quite awhile. Thanks in advance for any ideas.
    I am by no means a pool expert since I have only had a new pool for a couple of months, but have your pool store test for phosphates in the water. I was getting chlorine readings but literally hours later after shocking the chlorine would be almost gone. The pool store said things looked good, but told me to dump an entire bottle of stabilizer in. After that, chlorine would not read even after 2 pounds of shock and 1 crushed up tablet. Thats when i read up on chlorine block and learned that too much CYA from stabilizers cause this. I went back to the store. They tested my my CYA and it was somewhere in the low 50's and they said that was good so they were stumped for a few minutes because they also were getting no chlorine reading and there was so much in the sample that they could smell it. They finally tested for phosphates and they were very high which they said will cause no or very little chlorine readings. I put in 48 ounces of phosphate remover 48 hours ago and it is now crystal clear. I am taking a sample down again later so they can check phosphate levels and if good then its shock time gain too see if we get readings now.

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    Mod Squad JohnT's Avatar
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    Re: Is Chlorine block a real thing?

    Quote Originally Posted by rlgsmg3798 View Post
    I am by no means a pool expert since I have only had a new pool for a couple of months, but have your pool store test for phosphates in the water. I was getting chlorine readings but literally hours later after shocking the chlorine would be almost gone. The pool store said things looked good, but told me to dump an entire bottle of stabilizer in. After that, chlorine would not read even after 2 pounds of shock and 1 crushed up tablet. Thats when i read up on chlorine block and learned that too much CYA from stabilizers cause this. I went back to the store. They tested my my CYA and it was somewhere in the low 50's and they said that was good so they were stumped for a few minutes because they also were getting no chlorine reading and there was so much in the sample that they could smell it. They finally tested for phosphates and they were very high which they said will cause no or very little chlorine readings. I put in 48 ounces of phosphate remover 48 hours ago and it is now crystal clear. I am taking a sample down again later so they can check phosphate levels and if good then its shock time gain too see if we get readings now.
    Welcome to TFP!

    You have been what we call "Pool Stored". Phosphates have zero connection to your chlorine problem. What you need is to add chlorine more often.
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