Confusion about CYA and unstablized chlorine


Oct 3, 2018
I have read that it's best to add unstablized chlorine at night to prevent UV from degrading it quickly. But if a pool has the appropriate level of CYA, does it matter at what time the unstabilized chlorine gets added?


TFP Expert
LifeTime Supporter
Jun 12, 2009
NW Ohio
Doesn't really matter. Quite a few TFP'ers like to add in the evening so there is no UV on the pool for several hours, but it is also the case that for many of them the evening is the most convenient time to add anyway.

Bottom line is to not allow your FC to drop below the minimum for your CYA, per the FC/CYA Chart. As long as you are doing that then when you dose chlorine is moot.
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