CYA and tri-chlor

[chem geek]

The answer depends on the size of the pucks. They come in both 8-ounce and 7-ounce and 6-ounce 3" tablets (of varying thicknesses), 3-ounce 1" tablet, and 1-ounce 1/2" tablet. I'll use the 8-ounce 3" tablet for the calculations (that's why I use when I start out with Trichlor to add CYA).

1 puck adds 5.5 ppm FC and 3.3 ppm CYA in 10,000 gallons. This would mean 14 x 3.3 = 46.2 ppm CYA per month in 10,000 gallons. You didn't say the size of your pool so you'll probably need to scale this number down accordingly for a larger pool.

If you have a DE or sand filter that you clean/backwash regularly then this will dilute the pool water so you won't have as much buildup. Same for rain that overflows the pool or for splash-out.

If you let the CYA get higher, you'll have to raise the FC level (see Ben's Best Guess CYA chart) or you'll have to drain/refill periodically to keep the CYA lower or you'll have to use an algaecide (PolyQuat 60) to prevent algae (the latter option being more expensive).

You say you start with 0 ppm CYA after the winter. Do you let your chlorine go to 0 ppm FC over the winter or do you maintain the FC level? If you don't add chlorine, do you find that you have to use a lot of chlorine to clear your pool on opening? Does it have algae upon opening?

Richard