I know you need to drain water and add fresh water to reduce cya. Does it also go down when water evaporates? On a hot day I lose an inch of water. When I add fresh water am I lowering the cya as if drained and filled? Thanks.
No, the CYA stays in the pool, it does not evaporate. When your poo level goes down due to evaporation the CYA level actually goes up, but it is such a small amount it really can't be seen in the testing.
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