New to BBB and have a question about Best Guess Chart

[Armytiger]

I understand the chart in terms of for the given range of stabilizer I should maitain my FC at the respective levels; however, I do not understand what the 'shock' or +shock+ numbers mean or what the " ' " and "+" means? If my pool is not at the prescribed levels how do I calculate how much bleach to add to my pool to raise the FC levels?

[PoolDoc]

Hi Army . . .

+ The 'shock' level is what you need, say after a party or at first hint of algae. The +shock+ level is what you may need is the algae kept 'hinting' AFTER you boosted to the shock level, or when there's a problem that won't go away.

+ Calculating doses is based on ppm -- parts per million, or more to the point, pounds of stuff per million pounds of pool water.

Example: A typical 75' smallish community pool has 120,000 gallons, or about 1,000,000 lbs of water (8.3#/gallon). Stabilizer is 100% active, so if I add a pound of stabilizer to that pool, I get a 1 ppm (ie, 1# per millon #'s) increase in CYA. On the other hand, since diclor is either 55% or 62% active, I get about 0.6 #'s of stuff per pound of dichlor. So . . . to add a 3 ppm dose of CHLORINE to that same pool I need 3/0.6 #'s or 5#'s of dichlor.

Example 2: Say I have an Intex pool with 5,000 gallons. 5,000 gallons is 41,500 #'s or 4.2% of the million pound community pool. So it has a "pool factor" of 1/0.0415 or 24. The "Pool Factor"is what you multiple your stuff with, to find your dose. On this Intex pool, each # of stabilizer will add 24 ppm of CYA.

Method:
#1 - find your Pool Factor, and write it down. (PF = 120,000 / [your pool gallons]). The PF for a 10,000 gallon pool is 12.
#2 - find the active % of the chemical you add. 6% household bleach is, well, 6% active.

If you want ppm per unit dose (say, ppm per gallons of bleach) do this:
#3 - PF x Active% x dose pounds, like this for our 10K gallon pool: 12 x 0.06 x 8.5 (lbs per gallon of bleach) = 6.12. So, a gallon of plain household bleach adds about 6ppm of chlorine to a 10K gallon pool.

If you want to add a particular ppm to a particular pool, do this:
#3 - PPMd (PPM desired) is say, 15 ppm 'shock' dose, and say you've got dichlor. Here's the calc; (PPMd / PF) / Active% = dose pounds, like this: (15 / 12) / 0.6 = 1.25/0.6 or 2.01.
SO . . . you need 2# of dichlor to shock a 10K pool

Ben

[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.