First, I want to start by saying that I have reduced my CYA over the last year to 35ish, and I am doing a trial run on liquid chlorine only; however, I am puzzled by some calculations.
The label to my 3" Chlorine tablet container indicates 5.495 ppm of chlorine per 10,000 us gallons and recommends 2 tablets per week.
Assuming CYA is 30, Min FC is 2.25, and an avg of 2 ppm FC loss per day, 2.95 tablets would be required to last 7 days. Even reducing the week to 5 days with a min FC loss of 2 still requires 2.18 - 2.23 tablets.
The only way I can get their recommendations to match was assuming:
- 1.8 ppm FC loss / day, 5 days / week, and a Min FC of 2 ppm
- 1.75 ppm FC loss / day, 5 days / week, and a Min FC of 2.25 ppm
- 1.25 ppm FC loss / day, 7 days / week, and a Min FC of 2.25 ppm
I can't imagine a 1.25 ppm FC loss / day as being normal; so, I am leaning towards the 1.75 ppm FC loss at 5 days, but I guess the next question is, what would be a normal FC loss / day? I use to see anywhere from 1.5 - 2 ppm when using the tablets, but now switching to liquid I am seeing 2-3 ppm.
My reasons for trying to perform these calculations is that I am thinking a combination of tablet & liquid chlorine is best since it will add some CYA at a much slower rate, removing my need to buy stabilizer. It will also reduce my dependency on liquid chlorine so that I can get some of my garage space back, because even using 12% 1 US GAL liquid chlorine requires a lot of space / trips to the store for a 4-month pool cycle.