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Thread: using Bleach as chlorine question

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    j_m_min's Avatar
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    using Bleach as chlorine question

    I am not sure how adding bleach as chlorine relates to how fast it dissolves.

    Say that I need to add 1/2 gallon of bleach per day to maintain a 3ppm FC.

    If I add 1 gallon of bleach on day 1, will my FC still be 3 at the end of day two? Will it be 6 after day one and then 3 after day 2?

    Or would it dissolve more since it is all in the sun for a day?

    I guess I am not sure how the chlorine getting destroyed by the sun works?
    25,000 IG plaster pool. DE Pentair 60 gallons. Hayward pump with Single speed AO Smith 2.4 hp motor. Pool installed probably 20 yrs ago. Taylor water tesing kit.

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    Re: using Bleach as chlorine question

    Bleach does not "dissolve"

    Overly simplified:
    Your CYA level sets the % of the FC that will be lost to the sun each day. The higher you raise the FC level, the more ppm that will be lost each day (the % loss stays roughly the same).

    So if you try to raise the FC extra high so that you only have to add every few days, you will end up using more bleach in total due to higher ppm losses to the sun.
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    Re: using Bleach as chlorine question

    OK to there is more chlorine lost when the pool is at 6 FC, then when it is at 3 FC. Correct? THe amount of chlorine lost increases as the amount of FC goes up.

    My CYA is 30.
    25,000 IG plaster pool. DE Pentair 60 gallons. Hayward pump with Single speed AO Smith 2.4 hp motor. Pool installed probably 20 yrs ago. Taylor water tesing kit.

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    Mod Squad jblizzle's Avatar
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    Re: using Bleach as chlorine question

    That is correct. And the lower the CYA, the higher the % of FC that will be lost to the sun.

    In TX, I would think you would want to be closer to 50ppm for your CYA.
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    Re: using Bleach as chlorine question

    Well if you have no cya, any FC you have can be depleted within hours in the sun, so it makes sense extra over the target based off of cya is just throwing it away. Thanks jblizzle.
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    Re: using Bleach as chlorine question

    Any thoughts on when the best time to add chlorine to make it the most effective? I know that it will last longer in the dark, but who runs their pump in the dark?

    So far I typically wake up with 2.4 FC and add a half gallon of 8.25 bleach and then wake up with about 2.4 FC. I am not sure what is going on with FC when I am not home. I can only assume it goes up to some point and then comes down.
    25,000 IG plaster pool. DE Pentair 60 gallons. Hayward pump with Single speed AO Smith 2.4 hp motor. Pool installed probably 20 yrs ago. Taylor water tesing kit.

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    Mod Squad jblizzle's Avatar
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    Re: using Bleach as chlorine question

    There are VERY slight advantages to adding the chlorine in the evening, but it really does not make any difference. Just make sure it stays above the minimum.

    Some people have cheaper power at night and thus run the pump at night.

    BTW, use 10ml of water for the FAS-DPD so each drop is 0.5ppm
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    Re: using Bleach as chlorine question

    I figure 50 in Houston would be better but I go out of town, quite a bit and was saving the extra CYA so I can run the dichlor tablets in my chlorinator. Or do you think I should get it to 50 now. I can just run tablets until it gets there no big deal. Plust its not too hot here yet. 80s.

    - - - Updated - - -

    Does it help to prevent algae to run filter during the day as opposed to at night? I don't care when it runs. Just want it to be the most effective?
    25,000 IG plaster pool. DE Pentair 60 gallons. Hayward pump with Single speed AO Smith 2.4 hp motor. Pool installed probably 20 yrs ago. Taylor water tesing kit.

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    Re: using Bleach as chlorine question

    Ah, if you are saving a buffer for use of tablets, that is fine. They are likely trichlor and not dichlor.
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    Re: using Bleach as chlorine question

    Does it help to prevent algae to run filter during the day as opposed to at night? I don't care when it runs. Just want it to be the most effective?

    You are right. Trichlor.
    25,000 IG plaster pool. DE Pentair 60 gallons. Hayward pump with Single speed AO Smith 2.4 hp motor. Pool installed probably 20 yrs ago. Taylor water tesing kit.

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    Mod Squad jblizzle's Avatar
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    Re: using Bleach as chlorine question

    There are VERY slight advantages to having the pump run during the day.

    See how my last two statements seem contradictory

    Better for the chlorine to add at night less loss from the sun initially.
    Better for algae prevention to run pump during the day so no localized areas drop FC too low.

    Again the differences are so minor it does not really matter.
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    Re: using Bleach as chlorine question

    It's preferable to have periods of circulation throughout the day.
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    Re: using Bleach as chlorine question

    Thanks people
    25,000 IG plaster pool. DE Pentair 60 gallons. Hayward pump with Single speed AO Smith 2.4 hp motor. Pool installed probably 20 yrs ago. Taylor water tesing kit.

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    Re: using Bleach as chlorine question

    Your best algae preventative is chlorine and making sure you have enough of it every day.
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    Re: using Bleach as chlorine question

    Is 3 FC the minimum your chlorine should be or is that a target max? The reason why I am asking is because obviously this number goes up as you pour bleach in and gets depleted throughout the day. My FC every morning is around 2.4. But after I pour a half gallon of bleach in, my FC is close to 5. Is this normal? Am I doing this right?
    25,000 IG plaster pool. DE Pentair 60 gallons. Hayward pump with Single speed AO Smith 2.4 hp motor. Pool installed probably 20 yrs ago. Taylor water tesing kit.

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    Re: using Bleach as chlorine question

    Quote Originally Posted by j_m_min View Post
    Is 3 FC the minimum your chlorine should be or is that a target max? The reason why I am asking is because obviously this number goes up as you pour bleach in and gets depleted throughout the day. My FC every morning is around 2.4. But after I pour a half gallon of bleach in, my FC is close to 5. Is this normal? Am I doing this right?
    What is your CYA? Your minimum and target FC numbers are determined by your level of CYA. See this chart for the numbers.
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    Re: using Bleach as chlorine question

    My CYA is 35

    - - - Updated - - -

    My understanding is that when the bleach is entered, the FC levels will be their highest. Each day FC should go up and down if you are not using pucks in a chlorinator. So is the mininum and target FC numbers is that at the highpoint, or low point or constantly through the day? I am thinking that FC gets used up as the day goes on and the sun shines. So for me to maintain a 3 FC over a 24 hour period, my FC is going to have to be above 5 at some point during the day.
    25,000 IG plaster pool. DE Pentair 60 gallons. Hayward pump with Single speed AO Smith 2.4 hp motor. Pool installed probably 20 yrs ago. Taylor water tesing kit.

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    Re: using Bleach as chlorine question

    There are a couple of goals when chlorinating your pool.

    #1 never let the FC level fall below the minimum for you CYA level. Or algae can start growig quickly.
    #2 add enough FC whenever you do so that at the end of the day after the sun is off the pool you are still above the minimum

    The FC/CYA chart has 3 numbers on it. Minimum, target and shock. It is fine to chlorinate above the target if your consumption is high due to pollen, bather load, sun, whatever. It is safe to swim as long as FC is bel0w shock level. If you aren't going to be able to test and add for a couple of days you can go up to shock level and let it drift down over a couple of days.

    The most helpful thing is to test regularly and write it down. This will give you a record to review and understand chlorine usage patterns in your pool.

    Again, never let the FC level drop below the min. ever. Or you will be starting another green pool thread!
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    Re: using Bleach as chlorine question

    Yes, the FC is highest right when you add the bleach and then is will drop due to losses to the sun and anything in the pool.

    The minimum is the most important number to stay above. You need to raise the FC high enough that it is still above the minimum the next time you test and add more bleach. If you have been targeting 5ppm and it is dropping to 2.4ppm ... then you should try targeting 6-7ppm to stay above 3ppm.

    Also, use 10ml of water for the FAS-DPD so each drop is 0.5ppm ... saves your reagent.
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    Re: using Bleach as chlorine question

    Quote Originally Posted by j_m_min View Post
    My CYA is 35

    - - - Updated - - -

    My understanding is that when the bleach is entered, the FC levels will be their highest. Each day FC should go up and down if you are not using pucks in a chlorinator. So is the mininum and target FC numbers is that at the highpoint, or low point or constantly through the day? I am thinking that FC gets used up as the day goes on and the sun shines. So for me to maintain a 3 FC over a 24 hour period, my FC is going to have to be above 5 at some point during the day.
    That's pretty much it, though if you're starting with a 2.4, you are already too low and not adding enough bleach during the day. As others have stated, minimum FC for your CYA level is 3. Anything below is asking for trouble.

    My CYA level is about the same as yours. I test usually in the mornings during weekdays and keep my FC right around 5ppm (4.5 - 5.5). The pool loses about 1ppm/day during the spring (will start losing more in the summer), so I add about 1 pint. So in the morning and possibly into the afternoon, the pool is at 6ppm (or maybe a bit more) , but I know it will use it up with sunlight and leaves and such.

    As an FYI, I've always tried to shoot for the middle of the FC range (which in both our cases would be 3 - 7ppm range). I've not had anyone complain about red eyes, dry skin, fading swimsuits or the like. You should be safe to raise your FC up by 2ppm (which should put you at about 4.5) and maintain at that level.

    If you don't feel comfortable dumping the half gallon it at one time, add 1/4 gallon in the morning and 1/4 towards the evening. It should accomplish the same thing.
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