I don't want to drain it until the winter when I retile and resurface the pool. It is an inground gunite pool 20 yrs. old with a large sand filter...

The best I can tell is that the cya is 150. That is what I deduct from the PS234 test and the reading from one local store. I took it to a major chain store and they said it was 235! So I will base the chlorine on the 150. This is my first pool and I have been using the trichlor pucks for 2.5 years, after I had the pool refilled.
I just checked the pool and the Cl is at 10. I will take it up to 25 in a few minutes. Thanks for all your help.