We bought a new house last year with an in ground concrete pool (20,000) and constantly struggled all last year to keep any chlorine in it. Took the water multiple times a week to the pool store for testing and help and they continually told us our phosphates were too high (1,000 and above) and that was our issue. Week after week, we spend a fortune on phosphate removers, dealt with the constant clean up from them, back washed and then we were constantly paying to truck in more water from back washing so much because the filter would get clogged after the phosfree. Every week the pool store would still say our phosphates were too high, that was our issue and this continues until we closed the pool with very little time spent actually swimming. So, needless to say it wasn't what I thought the summer was going to be. We researched a bit and thought this summer would be better. It was ok for the first few weeks we opened, water was crystal clear, leveled were ok, then we started to have trouble holding chlorine again. After reading a bunch of these forums (thanks especially to chemgeek!!!) we realized that our cya has always been in the 100-200 range so we were never adding enough to begin with or shocking to the correct level. We have partially drained the pool once, which brought our cya from 141-124, plan on doing another partial drain however our water table is so high here, even that little drain caused the pool to pop out of the ground 1/4 of an inch 😬. We are hoping that we can get it down to the 80-100 level which I understand is still too high but it's better than we are at. Our biggest problem was, we bought all the chemicals off the old owner and both the pucks and the shock had cya in it. So for now we aren't using either, got liquid chlorine, and slamed finally to the appropriate level to stop losing everything overnight. I guess my question now is how to I properly maintain the chlorine levels (13.6 fc until we can drain and truck in some more water) thought the day (our pool gets full sun all day) without using pucks? Should we start out the day high and then add even night? Once again, totally new to this pool thing and just would like to be able to use it this year while keeping my little ones safe. Thanks in advance!!!