Waterbear and Mshumack,

I'm not so sure that higher CYA levels will consume more Bleach, They will require you to hold your FC at a higher level to be effective, but I'm not sure it will actually consume more.

If your CYA is 30. you will keep your FC normally around 3ppm. Let's say 1 gal of bleach would raise your ppm by 2, so when your FC goes to 2ppm, you put in a gallon and your FC now is 4ppm.

Now your CYA is 90. You will keep your FC normally around 7ppm. That same gallon of bleach now raises your FC to 9ppm. You're not consuming more, you are simply holding a higher PPM number to make the Cl more effective.

I'm not sure anything definitive has been determined on that subject, but that's been my anecdotal experience.

Dave S.