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
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