CYA Oddly Low / C3 Tablets

[cznkane]

Closed the pool at the end of last season with about 50 CYA. Drained maybe 25% of the water as part of my winterization. Refilled and opened it back up about a month ago. Assumed I would have, say, 25% less CYA (about 35-40). Measured yesterday and I appear to have near 0. Would love thoughts on how that happened.

As well, I've got a whole bucket of C3 3" tablets that are "99% Trichloro-S-Triazinetrione with 90% Available Stabilized Chlorine". I believe these have CYA in them, just tossed 6 in a floater and curious if there's a formula / calculator to tell me how many of these tablets will bring about 17,000gal of water up to about 50 CYA.

 

[mknauss]

As long as the pool water holds some FC, then add some stabilizer to get to 30 ppm. Then you can use the trichlor with the SWCG to get to your goal CYA and maintain proper FC levels.
Use Effects of Adding in Poolmath.
Each 8 oz trichlor tablet adds 3.2 ppm FC and 2 ppm CYA to your pool water.

 

[cznkane]

As long as the pool water holds some FC, then add some stabilizer to get to 30 ppm. Then you can use the trichlor with the SWCG to get to your goal CYA and maintain proper FC levels.
Use Effects of Adding in Poolmath.
Each 8 oz trichlor tablet adds 3.2 ppm FC and 2 ppm CYA to your pool water.

Thank you! I knew that was in the app somewhere, was looking at the CYA card and didn't see it. My plan (hope) was to use the tablets to raise my CYA the necessary amount but sounds like that might be a bit slow going. The 6 tablets in there will likely take a week to dissolve in the floater and only add 12ppm CYA. I'll go run down some CYA and get it in a sock in front of the return jet.