Quick history: Last year, out of the blue, pool turned green. I had no idea what I was doing, so I added puck after puck and bag after bag of shock, probably 30lbs of shock at least in total. As you probably can guess, I couldnt get ahead of the algae. I ended up finding TFP and reading tons about BBB and how to kill the algae. I bought a TF1000 and found out my CYA was through the roof, among other things. I drained the pool (11000 gals) almost completely, leaving maybe 1000-1500 gallons in the pool. I filled it back up, followed the procedure of shocking and checking overnight chlorine loss for several days until I believed all the algae was dead. To my dismay, the CYA level still reads higher than the TF1000 can measure, the dot is no longer visible well before I reach the highest ppm graduation on the container. Ive added borates and maintained chlorine level with bleach since then (about 6 mo).
Fast forward to today:
Water temp: 65F
total chlorine: targeting 11ppm (based on CYA 120)
pool is 11000 gals, with pebbletec finish, cartridge filter, heliocol solar, a pool frog with the mineral pack (no longer using chlorine tablets), and a lectro pure magnetic water conditioner.
Water is clear, no apparent algae growth. Pool water was as cold as 38 degrees for several days over winter (everything should be dead, right?)
Now, for my questions:
1) How often I should be expecting to add chlorine? We arent even at full summer temps here in Tucson and I lose several PPM overnight. If i dose the chlorine level to 11ppm, the next day its around 6-8ppm. I realize that with so much CYA I pay a penalty by having to hold my levels higher, but shouldnt all that CYA be helping me keep the chlorine in the pool overnight? With a very high CYA, 120+, how much available chlorine loss should I expect from day to day?
Is this quick drop in chlorine a symptom of another problem that I haven't read about yet?
2) Does it seem realistic that I could empty a pool that had a huge (unknown) CYA 85%+ (about 1000 gals left) and refill it with tap water to 11000 total, and still have a CYA of 120+? I'm trying to avoid draining the entire pool again this season, but if the daily chlorine loss from #1 above is so great, I may have to.
thanks very much for the help - this forum is a fantastic, well beyond the garbage the local pool store has tried to feed me. - andy