It's a standard rule in the pool industry to parrot the fiction that chlorine levels over 3ppm aren't safe.

This comes from either the EPA or FDA saying that something like 25 or 30 years ago, but the same agency also said it was unsafe to drink water with chlorine levels over 4ppm!

So, according to the parroted fiction, if your water is has 4ppm of chlorine you can drink it, but you can't swim in it! See the irony?

CYA inhibits chlorine's action so the safe maximum level for swimming varies depending on the CYA level.

There's quite a discussion going on in the China Shop right now about safe chlorine levels that are documented scientifically. It's tough to follow, but it's VERY informative.