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Thread: Too much bleach when shocking?

  1. #1
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    Too much bleach when shocking?

    In pool school it says that when shocking your pool that too high an FC is not good because it might damage equipment.

    But what effect does a bit more bleach have?

    If you were aiming for a FC of 16ppm, is there any harm putting and extra half gallon or so of bleach in?

    Is it a waste of bleach?
    13,000 gallon; sand filter; inground; fibreglass; pump not sure yet (need to check); Installed over 12 months ago.

  2. #2
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    Re: Too much bleach when shocking?

    Like most things in life, the answer is not black or white. We provide guidelines.....not absolute dictates.

    If the doctor suggests two aspirin, you can be pretty sure that 1.75 - 2.25 aspirin will not cause you to grow extra appendages.

    Then why not 3 aspirin? 4? 16? or maybe 1 will be as good??

    BBB is obtaining the knowledge to understand why the parameters we test are important, understand what to do about them when they are outside of the norm, and understanding how to adjust back inside the norm.
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  3. #3
    Mod Squad Smykowski's Avatar
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    Re: Too much bleach when shocking?

    Quote Originally Posted by juzzie
    But what effect does a bit more bleach have?

    If you were aiming for a FC of 16ppm, is there any harm putting and extra half gallon or so of bleach in?

    Is it a waste of bleach?
    Since it is possible to shock higher to take care of Mustard Algae, yes, more bleach than normal shock is ok. However, simply an "extra amount of bleach" is not a good idea, because BBB is about purposefully putting chemicals in your pool because it needs it.

    When I shocked my pool at the beginning of the year, I determined my shock level, and then targeted 2-3ppm above that. By doing this I made sure I stayed above shock level at all times to get the process done quickly. At the same time, I safely stayed under the Mustard Shock level to protect my liner and equipment.
    TFP Moderator33' round, 23,000 gal AG vinyl , 1.5HP PowerFlo Matrix downsized with 3/4HP impeller (X2), Hayward S180T 150# sand filter (X2), Hayward H250 NG heater
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    Re: Too much bleach when shocking?

    Quote Originally Posted by Smykowski
    Quote Originally Posted by juzzie
    But what effect does a bit more bleach have?

    If you were aiming for a FC of 16ppm, is there any harm putting and extra half gallon or so of bleach in?

    Is it a waste of bleach?
    Since it is possible to shock higher to take care of Mustard Algae, yes, more bleach than normal shock is ok. However, simply an "extra amount of bleach" is not a good idea, because BBB is about purposefully putting chemicals in your pool because it needs it.

    When I shocked my pool at the beginning of the year, I determined my shock level, and then targeted 2-3ppm above that. By doing this I made sure I stayed above shock level at all times to get the process done quickly. At the same time, I safely stayed under the Mustard Shock level to protect my liner and equipment.
    "When I shocked my pool at the beginning of the year, I determined my shock level, and then targeted 2-3ppm above that. By doing this I made sure I stayed above shock level at all times to get the process done quickly."

    You have answered my question pretty much spot on. What I was getting at I suppose is if you are at the start of the shocking process and you are targetting 16PPM. Let's say you know your FC level is going to drop down from 16PPM to 6PPM. Then if you dose up with bleach to get to 18PPM the chlorine is still going to consume the same amount of baddies by the time the shocking process is complete and you haven't wasted any bleach by doing this?
    13,000 gallon; sand filter; inground; fibreglass; pump not sure yet (need to check); Installed over 12 months ago.

  5. #5
    Senior Member Richard320's Avatar
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    Re: Too much bleach when shocking?

    Quote Originally Posted by juzzie
    You have answered my question pretty much spot on. What I was getting at I suppose is if you are at the start of the shocking process and you are targetting 16PPM. Let's say you know your FC level is going to drop down from 16PPM to 6PPM. Then if you dose up with bleach to get to 18PPM the chlorine is still going to consume the same amount of baddies by the time the shocking process is complete and you haven't wasted any bleach by doing this?
    A couple PPM isn't going to make much difference. However, UV degradation is a percentage of FC, not a fixed amount each day. So grossly overchlorinating will cause more ppm FC to be lost to sunlight, and is wasted.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
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  6. #6
    Mod Squad Smykowski's Avatar
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    Re: Too much bleach when shocking?

    Quote Originally Posted by juzzie
    Let's say you know your FC level is going to drop down from 16PPM to 6PPM. Then if you dose up with bleach to get to 18PPM the chlorine is still going to consume the same amount of baddies by the time the shocking process is complete and you haven't wasted any bleach by doing this?
    Couple things. The scenario above is a little extreme, because you shouls be testing more often during shocking to avoid that drop.

    To get to the heart of your question, yes, the higher the FC level, the higher the loss rate due to sunlight. However, if you're shocking, it's because there's something in the water. I would suspect that the loss rate from letting the yuck regain a hold because you let the FC drop is higher than the accelerated rate due to the higher target level.
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    Pool Store year 1 - $850 for 2 months; Pool Store year 2 - $440 for 2 months, TFPC year 1 - $170 for 4 months; TFPC year 2 - $95 for 4.5 months
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  7. #7
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    Re: Too much bleach when shocking?

    Quote Originally Posted by Richard320
    Quote Originally Posted by juzzie
    You have answered my question pretty much spot on. What I was getting at I suppose is if you are at the start of the shocking process and you are targetting 16PPM. Let's say you know your FC level is going to drop down from 16PPM to 6PPM. Then if you dose up with bleach to get to 18PPM the chlorine is still going to consume the same amount of baddies by the time the shocking process is complete and you haven't wasted any bleach by doing this?
    A couple PPM isn't going to make much difference. However, UV degradation is a percentage of FC, not a fixed amount each day. So grossly overchlorinating will cause more ppm FC to be lost to sunlight, and is wasted.

    Yeah good point.

    What you are saying is overchlorinating = more loss of FC due to UV = waste.

    If I'm running late for work I'd probabley rather throw a bottle in and keep the shock process going if I don't have time to test.

    I suppose the BBB method would say not testing = [potential] waste!
    13,000 gallon; sand filter; inground; fibreglass; pump not sure yet (need to check); Installed over 12 months ago.

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