Quote Originally Posted by smallpooldad View Post
Would you know, or anyone else, how much 21 ozs of Algaecide 60 drop the chlorine ppm by in a 20,000 gal pool?
This post talks about the relationship where a 2.2 ppm FC drop in 10,000 gallons occurs with the dose of 10 ounces PolyQuat 60 in 10,000 gallons. So you can roughly scale up accordingly, though that's a LOT of PolyQuat. To drop 10 ppm FC would take 45 ounces of PolyQuat 60 per 10,000 gallons.

If they have CYA in the water, then I wouldn't be afraid of going into the water even with 24 ppm FC though it would be preferable if their dogs not drink large volumes of water (it's not a problem for a single exposure but if they drank every day at this level then that would not be good). In terms of disinfection and oxidation of skin, swimsuits and hair, it's still far less "active" chlorine than found in indoor pools. 24 ppm FC with 40 ppm CYA is equivalent to 1.5 ppm FC with no CYA. Also, the FC should drop in sunlight reasonably quickly -- probably from 24 to 16 in one day of strong sunlight.

Richard