Normal readings . . . CYA of 50 . . . FC holding overnight . . . losing appx. 4ppm FC during the day? What's considered 'normal' loss in a direct sun situation? Requires appx 3 - 96 ouncers a day to bring back to target.
How to account for this?
- Thread starter Rangerman
- Start date
How normal your loss is depends on what FC level you are starting at. With CYA at 50 you can expect to lose about 50% of your FC level each sunny day, a little more if the pool gets direct sunlight the entire day.
Losing 4 ppm from a starting point of 5.7 is not normal and suggests that something is growing in the water. It sounds like it is time to shock the pool.
Holding overnight is strange when there is such a large loss during the day, but suggests that whatever is using up the chlorine may be growing during the day. So this could be a nascent algae bloom. As Jason stated, try shocking the pool and then see how things go after that. Perhaps you've got a hole in the ozone layer directly above your pool 
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