Cya 100 + ?????

[PoolDoc]

One thing to note, is that at CYA of 100 or more 4ppm fc is not effective at killing algae and you will get a green pool eventually. You need to keep the pool at at least 8ppm (somewhere between 8 and 15) and you'd have to take it up to 25ppm to "shock".

The Best Guess chart page explains this.

Also, with a PF:7, your pool's FC (free chlorine) will be increased by 7 for each pound of chlorine gas equivalent added -- 1 gallon of 6% (chk %!) is about 0.5 lbs equiv, so will add about 3.5 ppm per gallon or 2.6 ppm per 96oz jug.

With a CYA of ~120, a dose of 3 gallons (4 96oz) would be a good start, possibly followed by 1 96oz jug per day, till you hit 20 ppm. Then, back off and hold in the 12 - 15 ppm range.

With CYA > 100 ppm, 20 ppm is NOT too high to swim. I've been running a large (>200,000 gallons) country club pool all summer at CYA in the 70 - 110 range (leaks a lot) and FC in the 8 - 20 ppm range . . . with NO complaints whatever.

Thanks for the lifetime subscription!

[macox126]

Thanks to all for the help.

[Watermom]

Just adding my thanks as well. A lifetime subscription is a big help to the forum! Hope you enjoy being a member!