I recently noticed I was having to add an unusual amount of chlorine in order to get much of a FC reading on my kit (prior to this we had record rainfall, 10" or more over a 5 day period). During this rainstorm, I backwashed probably 1200 gallons or so out of the pool. I have a couple stains that were in the pool prior to me purchasing the home that only show when PH is low. Seeing these, I checked the balance. PH was low. FC was almost non-existent. CC was higher than FC. CYA seemed normal. So I shocked it with trichlor shock. I added chlorine to my pool as normal and continued. As the FC dropped from the shock, I noticed it kept falling even though I had 2 3" pucks in the chlorinator (15,000 gal pool - small). I am only running my pump about 4.5 hours over the winter time in Alabama (because it worked fine last year - no algae). I took a sample to my pool store today and the CYA was around 144, FC at .75, CC at 1.0. They recommended I put a pound of Calcium Hypochlorite (73%) to shock and get rid of the CC. I thought I did that last week with the trichlor (2 lbs). I suppose the CYA has gotten too high and now is requiring a lot of chlorine? Can you tell me if you think using the GLB CalHypo is going to make a difference? Or should I just drop a hose in there and backwash half the pool out? Thanks.