How much Chlorine should I expect to use?

I'm new to the pool forums and new to the BBB method. I have a 12,000 gallon AG pool with a cartridge Filter. For the past 6 years, I've used the nature 2 system with a combination of tablet and granular tri-chlor. After reading much about that system here on the forums last year, I decided it was time for a change, and ran the last have of the season w/o the cartrige, but still using of the remaining chemicals I bought in the spring. My readings last night were the following
PH 7.8
CYA 40
TA 100
FC 3.0

This morning, my FC had dropped to 1.0. (I did not add any chlorine last night). The water is not crystal clear like I would expect it, but I can see the bottom of the pool without trouble.

Is there something in the pool that is affecting the water clarity as well as using up the FC?
How much chlorine should I expect to add on a weekly/daily basis in the scenario? I know it depends on so many factors, but I'm looking for a ball park that I can use as an indicator that something is wrong.

Thanks,

Mark

My pool is roughly the size of yours and my CYA is usually around 40ish. I typically add a couple of quarts of bleach per evening.

Since your pool isn't totally clear and your chlorine had dropped so low (with a cya of 40 you need to keep the cl between 3-6 all the time or you risk an algae bloom), I would suggest going ahead and shocking your pool up to about 15ppm this evening after the sun is off your pool. An hour or two after adding the bleach tonight, test it to get the cl reading. Then, test it again in the morning within 2 hours of sunrise. If you haven't lost more than 1ppm of cl overnight, then you can let the cl drift down but if you have lost more than that, shock it again. Repeat the cycle until you do not have more than 1ppm loss overnight.

Run your pump 24/7 while you are trying to get it clear. If, after you are past the losing more than 1ppm overnight cycle, it is still not super clear, you might try adding a little DE to your sand filter to increase its filtering capabilities. More about that here:

http://www.poolforum.com/pf2/showthread.php?t=3742

Welcome to the forum, Mark!

Thanks for the advice. The water is also now clear!