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Thread: what happens to all the extra chlorine after a shock?

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    what happens to all the extra chlorine after a shock?

    while my pool chemistry is about perfect at this time (thanks to this site) there is something I cant get past. I wonder if for example one has a TC of10 and a fc of 2 which would mean a CC of 8. If they shock the pool then obviously the FC and CC will change but doesn't then the TC (even if its all free) simply rise far too high? In other words do you end up with always having a high chlorine level? As the FC does its work and becomes CC then eventually you have to shock again. It just seems like this scenario will lead to a constant high chlorine level all the time.

    I will not be shocking my pool just for the heck of it but will only do so when the TC,CC,FC levels dictate that I should or if I have a problem that requires a shock. (I hope that's correct)

    But just a general curiosity about how would one get a chlorine level down to 2-4 if they are at say 10 and once in a while finding a need to shock because of too much CC building. It just seems like it would always all be high.

    Or (to guess an answer to my own question) does this have to do with CYA? Perhaps if CYA is at a proper level then the chlorine will dissipate and one should ever find them selves stuck at the 10 range. Does this make sense? and I hope I worded it well enough to be understood.
    Thanks

  2. Back To Top    #2
    Richard320's Avatar
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    Re: what happens to all the extra chlorine after a shock?

    Both CC and FC break down in sunlight.

    CYA acts as a sunscreen so it slows it down, but never eliminates it. That's why you have to add chlorine every day by some method. You will never find yourself stuck at some number. All you need is some UV sunlight and it starts dissipating.
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    BoDarville's Avatar
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    Re: what happens to all the extra chlorine after a shock?

    Richard and I are saying the same thing. Since I had this response keyed up, I'll go ahead and post it for emphasis on the importance of maintaining proper chlorine levels and why it needs to be replenished daily...

    Chlorine is consumed primarily by two things: Sunlight and Organics (bacteria, viruses, and other organic contaminates). Even in a clean pool, you will lose some chlorine to sunlight. In addition, organic contaminants are constantly trying to gain a foothold in you pool. Proper chlorine levels eradicate those contaminants before you ever notice them. For those reasons, you need to replenish chlorine daily to maintain the target level for your pool (see Chlorine CYA Chart).

    Combined chlorine (CC) is an intermediate breakdown product created in the process of sanitizing the pool. CC causes the "chlorine" smell many people associate with chlorine pools. CC indicates that there is something in the water that the FC is in the process of breaking down. In an outdoor pool, CC will normally stay at or near zero as long as you maintain an appropriate FC level. If CC's get too high, it's because the chlorine level dropped below what is considered minimum for your pool, according to the CYA level. If that ever happens, you would need to SLAM - Shock Level And Maintain. During a SLAM, higher levels of chlorine are added in order to oxidize all of the algae, combined chlorine, bacteria, viruses, ammonia, and other organic contaminates that may be present. Oxidization is a fancy word that means breaking down the organic molecules into smaller parts which are harmless. However, if you continually keep the chlorine level at the recommended targets for your CYA, you should never have to SLAM.
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    Re: what happens to all the extra chlorine after a shock?

    Thank you......so then any uv hitting the pool and you really cant end up with a runaway chlorine affect because it will always eventually dispate

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    BoDarville's Avatar
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    Re: what happens to all the extra chlorine after a shock?

    Yes, that is correct. You will notice a decrease in chlorine consumption in late summer and early fall since the days get shorter, the sun angle decreases, and the water gets cooler.
    Gold Supporter, TFP Lifetime Supporter, 26,680 gal Plaster IGP 3.5 - 10' depth / Attached Waterfall Spa, Manually Chlorinated, Triton Sand Filter, 1.5 HP * 1.1 SF = 1.65 SFHP 1-speed Pentair WhisperFlo WF-26 Pump, 400K BTU NG Teledyne Laars Series One Heater, Polaris 360, Test Kit Comparison, Chlorine/CYA Chart, SLAMing Your Pool, OCLT
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