New to BBB and have a question about Best Guess Chart

[CarlD]

I use a simpler but related method, that's only good for add bleach/liquid chlorine, that I call The Rule of Thumb:

1 gallon of 6% bleach adds 6ppm of FC to 10,000 gallons of water.
1 gallon of 5.25% bleach adds 5.25ppm of FC to 10,000 gallons of water.
1 gallon of 12.5% liquid chlorine adds 12.5 ppm to 10,000 gallons of water.

If you have 20,000 gallons, then you need 2 gallons to get the same effect. If you only use 1 gallon you'll get half as much FC.
If you have 5,000 gallons you need half as much (2 quarts) to get the same effect. If you use 1 gallon you'll get double the FC.

So, if you have 30,000 gallons, you need 3 gallons to get the effect of 1 gallon in 10,000 gallons.
If you have 15,000 gallons, you need 1.5 gallons (or 6 quarts) to get the effect of 1 gallon in 10,000 gallons.

If your pool in 13,000 gallons, you can use the 15,000 gallon approximation, etc.

NOTE: This does not work for dry chlorine forms like dichlor, tri-chlor and cal-hypo.

Carl

[Armytiger]

Thanks for the info and the equations. So if my CYA is 30ppm and I'm going to shock my pool. The chart says shock 15. Does this mean that I want to raise my cl levels to 15 ppm or a 15 ppm dose?

Dale

[Watermom]

You raise the chlorine up to 15ppm.

[CarlD]

So, if your FC is 0, or even .5, you'll add chlorine to raise it to 15, which will be adding 15

But if your FC is 6, you only want to add 9ppm of chlorine to raise it to 15.

Carl

[Watermom]

So, if your FC is 0, or even .5, you'll add chlorine to raise it to 15, which will be adding 15

But if your FC is 6, you only want to add 9ppm of chlorine to raise it to 15.

Carl

Uhhh ---- isn't that what I said above??

[CarlD]

I just wanted it to be clear for ArmyTiger that it depended on the starting point.

I was just a little less terse/cryptic!

Carl

[Armytiger]

Watermom . . . I understood

Thanks to both of you for your explanations.