Adding too much chlorine at one time?

[RGS]

Awhile back, I saw a reply that was in the middle of a thread on this forum, where someone commented on the idea of adding extra amounts of liquid chlorine so that you don't have to do it every day. I don't remember where it was, but the argument went something like this: a person was saying that he knew how much FC he should keep in his pool, in relation to the CYA level, but he didn't like the bother of having to add bleach every day, so he would add an extra large amount so that he only needed to do it every 2 of 3 days.

Someone else replied that you should add the right amount every day instead of an extra large dose every 2 or 3 days. The argument was that if you add too much chlorine at one time, the excess chlorine will not get bound to the CYA. Therefore the excess chlorine will burn off fast in the sunlight and just be wasted. That made me wonder if there is a rule of thumb, about how much of the FC in the pool gets bound to the CYA, so that one could know the amount above which the chlorine might be wasted.

I also recall a post from ChemGeek, where he said that the CYA in the pool also seems to act as a shield against UV, so that the FC in the deeper parts of the water seems to be protected from sunlight even if it is not bound to the CYA.

So I realize this is complicated, but just wondering in general about the idea of chlorine being wasted if we put in too much bleach and do it less frequently?

 

[ajw22]

That made me wonder if there is a rule of thumb, about how much of the FC in the pool gets bound to the CYA, so that one could know the amount above which the chlorine might be wasted.

That is all simplified into the [FC/CYA][/FC/CYA]

So I realize this is complicated, but just wondering in general about the idea of chlorine being wasted if we put in too much bleach and do it less frequently?

Go give it a test and see if it works. Enough folks have tried to find it does not.

Search is your friend.

 

[borjis]

Well, I do something kind of like that. I don't dose bleach daily. Never have.
And it has not been any kind of problem.

But I do not overdose. I only add the amount needed to reach max target.

My pool is covered most of the day on weekdays and I only have guests over on the weekend.
I'm also not in the lower south climates.

Because of these 3 factors, I get by just fine testing every other day (I know my pools needs) and
only adding a 1/2 gallon of 6% if needed to get to my max target of 8ppm for a CYA level of 50.
Occasionally it amounts to 9ppm but never over that.

It's not for everyone and if I lived in the southern regions where it is hotter/ more sunny I'd probably
have to test and dose daily.

 

[jblizzle]

One way to think about it is that the CYA will protect a % of the FC in the water ... the higher you raise the FC at a given CYA, the more ppm of FC will be lost to the sun each day.

Some made up numbers for an example:
CYA = 50pmm ... so lets say loss is 50% to the sun (no cover, lots of sun, etc) each day.
Minimum FC = 4ppm

Daily dose to target 8ppm so that 50% loss would drop to 4ppm.
Now you want to go 2 days, you can't just assume your daily loss is 4ppm, if you did you would add 8ppm to get to 12ppm.
Well the first day you would lose 6ppm (50% of 12) and the next day you would lose 3ppm (50% of 6) leaving you at 3ppm (below the minimum) and losing 9ppm to the sun (instead of 8ppm if you were dosing daily).
If you want to guarantee you stay above 4ppm, you would have to dose to 16ppm every other day ... which is a loss of 12ppm over 2 days (8ppm + 4ppm) compared to the 8ppm (4ppm + 4ppm) if you added daily.

The numbers are made up for simple illustration, but gets the point across.

 

[RGS]

That is all simplified into the [FC/CYA][/FC/CYA]



Go give it a test and see if it works. Enough folks have tried to find it does not.

Search is your friend.

I’m familiar with that chart, and use it all the time, but that is not at all what my question was about, The chart just tells how much FC you need to have in the pool, as a function of the CYA level.

My only question was about what happens to the extra chlorine if you add more than that amount at one time. It sounds like there isn’t a definitive answer - too many variables

 

[Derb22]

RGS. Jason exactly answered your question. Yes you will lose a larger % of FC TO burn off which cannot be bound by the CYA if you overdose the FC. But yes you can account for that loss and add more FC every other day.