Quote Originally Posted by themaccs View Post
So, with the bucket test thing I guess I am trying to create a mini version of my pool?
Yes, that is correct. It's just easier and less expensive than dumping a bunch of chlorine in the pool. If the amount left is huge, then water replacement could be cheaper/easier.

Your high chlorine demand at the end of last season when the CYA was still high was likely due to nascent algae growth since you'd have to maintain a much higher FC level to prevent that and have to shock at even higher levels. The water probably had lots of nutrients for algae as well. When you closed for the winter, the FC went to zero and bacteria had a great time dining on the nutrients in the pool including the CYA that was there. If the CYA dropped from 100 to 30 ppm, then that 70 ppm could get converted into around 20-25 ppm ammonia that would require roughly 200 ppm FC to get rid of. That's worst-case, but is an extraordinary amount of chlorine required to be cumulatively added.