Earlier this summer, my pool was doing great, with swg set on 20%, fc at 3, cc at 0, cya at 25.
After returning from one week vacation, I found fc at 0,cc at 0.5, and cya at 0, and a little algae on side wall of one corner of the pool. I bumped the swg to 40% and started adding 7 lbs of cya over the course of last 2 weeks, now reading 25. In addition to swg, I am also adding 10% liquid chlorine about a quart/day. Still losing fc like crazy, still no cc, with minimal green algae at one corner of the pool. Starting to think it's algae, not the lack of cya, or maybe both. Should I slam now, or wait til I get the cya higher? The pool water is still clear, but not as sparkling as it used to be.
Last night fc was 2.5 after adding half gallon of chlorine, this morning fc down to 0.5, with the swg running.
In four years of having this pool, have never slammed before, never seen chlorine used so rapidly.
Second question: I have read that cya doesn't get used up. I have never drained the pool since initial startup. Get occassional dilution from rain, but I use the automated cover during the off-season, pumping off the rain water from the top of the pool cover. So where did the cya go? Is there a real lifespan to cya? Does it become ineffective with 4 years of age?
Thanks for any help.