We will be opening our pool soon and have been testing the FC. We do not cover the pool in the winter and once a month we add some chlorine just to be safe. The water is crystal clear, but there is a lot of dirt on the bottom. I have dug the leaves out of the bottom and keep big debris out. Our winter has been very warm compared to other years. Water temp is still in the low 50's. Some gallons of the chlorine raise my FC up like normal, but others seem weak and don't do much of anything. I do not have the pump up and running so I'm mixing the water up by plunging my leaf skimmer up and down all around the pool until I have waves splashing. I test after I circulate the water somewhat. The OCLT comes out great with a loss of no more than .5. My combined chlorine is 0. What I'm wondering is, today, it was cloudy all day. My FC was 20.5 last night and 20 this morning. My CYA at the end of last season was somewhere between 35-40, so I'm using that as my number this year. I just checked my the FC and it's down to 14.5. Does that seem like a lot, since it was cloudy all day? I've been purchasing gallons of chlorine but would bet its leftover from last year's stock and wonder, even though this gallon brought my FC up like normal when I added it last night, if its old, will it degrade faster in the pool?