How Long will Chlorine Last if it is raised to 40ppm

[smallpooldad]

Using bleach, how long (days) will chlorine last if raised it to 40ppm before it goes to 5ppm in a 9000 gal pool. Assuming CYA at 38, ph 7.4. Currently using up about 1 ppm per day when kept at 5 or 6 ppm.

Thank you in advance for any replies.

[chem geek]

It depends on the source of your chlorine loss. If your current 1 ppm loss at 5-6 ppm comes completely from breakdown from sunlight, then the rate of breakdown at 40 ppm could be up to 8 times faster so around 7 ppm FC the first day, but would slow down after that. Breakdown from sunlight is proportional to the concentration of chlorine -- so twice the chlorine, twice the loss (ignoring a shielding effect from the chlorine itself that is small in pools with CYA).

Usage of chlorine from the oxidation of organics is dependent on how many organics are in the pool as well as the chlorine concentration. So this may increase at higher chlorine levels, but perhaps not as much as there is a limit as the organics go away by getting oxidized.

Anyway, let us know what you find as info from real pools is what is most relevant.

Richard