That probably is the post and I understand that small amounts need not be burned off with chlorine but I would also think that adding 6 PPM FC to a pool with 0.5 PPM CC will burn it off assuming that the CYA is at a low level.

As I said I never test for CC in the pool, only my spa but I guess in a situation like what I'm going through it might be worthwhile to test. But ...

... now more questions come to mind - Can CC really start accumilating if you are running high FC (8 - 10 PPM or more)? I would think not as anything under 1/10 of the chlorine you put in would be burned off (I am assuming that the pool started at 0 PPM CC and CYA is under 50). My pool was at 0 CC when I noticed I had no CYA.

How long do you need to keep a high chlorine environment? If you put in 10 PPM FC at 6 PM and you test at 6AM and have 6 PPM left, hasn't the chlorine done it's job. I always thought that as long as you have a FC residue that there isn't any more that the chlorine needs to do. (again CYA under 50). And wasn't the high chlorine in the tub burning off the CC as it was forming?

In my mind, a "shock" really isn't a specific quantity - it can be as low as 5 PPM FC or as high as 20 PPM FC, which is why I questioned the 15 FC figure for shock.

At this point with my pool not seeing a FC under 5 PPM since I started this post I would assume that any algea is dead. I actually put in 146 oz of bleach into my pool last night which yeilded 7 PPM chlorine added to what was there I was hovering around 11 to 13 PPM. I "shocked" the pool for the last time although I doubt there was a lot of CC in there.