Last year I found this site, and had the best water in 10 years of pool ownership-my cya was HIGH and with partial drains and fills, was able to manage a fairly high cya level for the summer (75). Now I am getting ready to open my pool, so I checked my cya level and its at ZERO. We've have flooding rains so I think that level is pretty accurate. My questions are: I'm using some pool test chemicals left over from last year to check cya-is it still good.I have to order more anyway, but wonder if old solution can affect reading. Also, should I have my pool opener but in the normal chems. they put in since I most likely need to raise my cya. I've never have to add cya and am unsure how and how much. THanks in advance for any advice