Why did my bleach leave?

[philanna]

Oh ya, should I leave my filter running untill my chloine level drops? Or should I let it run its normal cycle (8hrs per day) even though my CL is 20?

[chem geek]

It is possible that having your pump run 24/7 until the chlorine level drops might help make the chlorine level drop a little faster due to better mixing (bringing higher chlorine levels closer to the surface where it can get broken down by sunlight more readily), but this might be a minor effect. So the real answer is, "I don't know", but having your pump on might help and it certainly won't hurt (except for a somewhat higher electric bill). Once your chlorine is down closer to normal levels, you can return your pump to normal hours.

The main way to bring your chlorine level down is to keep the pool exposed to sunlight as that will break down the chlorine faster than most anything else.

Richard