Chem Geek,

I am not sure I am understanding this correctly but this is what I think you meant, please correct me if I am wrong.

Based on a number of 5% for and SWG for minimum free chlorine versus 7.5% for a regular liquid chlorine, etc. of the CYA level, etc. The required chlorine dosage would be 66.66% of what is shown in the "Chlorine/CYA Chart" for a non-SWG pool. Or would the percentage move higher say to 75% at Target FC, and 88% at Yel/Mstrd Min FC ?

For example at a CYA of 50 the settings for a SWG pool might be as follows: minimum FC = 3.7 (regular pool) x 0.6666 or 2.5, Target FC = 5.7 x .6666 or 3.8, and Yel/Mstrd Min FC = 7.5 x 0.666 or 5, for SWG pools.

Could the same calculation be applied to a SWG pool with a CYA of 30 (my pool), for example Target FC = 3.5 x .6666 or 2.3? At lower CYAs would this 66.66% conversion factor work as well? I personally think no but what do believe?

For information's sake: His pool is 20,000 gallons using a brand new (5 days old) Aquapure 1400 cell, set at a power level of 35%, he maintains the FC at 8, the CYA at 50, he is losing 1.09 ppm of chlorine a day, based on the Aquapure manual he produces 1.25 lbs of chlorine in 24 hours, and he runs his pool 10 hours per day. I hope this calculation is correct, but most probably wrong, it is based on a 1 ppm loss of chlorine being equivalent to 2.6704 ozs of chlorine required to replenish a 20,000 gal pool.

One other factor I failed to note is his pool is nearly 20 years old with the top plaster coat missing in many areas some of which have black algae. I told him he needs to drain the pool as it would require Hercules to treat the many spots while the water is in it, we could cover them with towels filled with pure chlorine and treat them together in one night by scrubbing every 30 minutes or so, but he is loath to do this. He is in his late 70's. The pool water is otherwise very clear.

This is why he may be using 1 ppm of chlorine per day instead of 0.5 ppm, but the UV index here, which is very high, may also be a factor.

Am I anywhere close on the numbers or am I hopelessly confused?

But what about turnover, which is also his concern. He could up his power setting to 50%, and reduce his run-time, a major concern of his as the KwH price is two to three times more expensive as the mainland, He and I would like to know what might be a good turnover number for the water, if you help with the turnover rate it would be greatly appreciated.