KirstenHW, bleach mixes very quickly with the water when you add it. I think a lot of people add bleach the way you are describing it and it isn't a problem. It's probably better to add it in front of a return, but I'd doubt you've hurt anything by just dumping it in.

chem geek, I appreciate all the math and stoichiometry you present in your posts. It has really helped demystify the chemical processes going on in my pool. (And a big shout out to Evan for the same thing.) I suspect this thread may be getting near the China Shop Event Horizon given Ben's desire to keep from scaring people with too much information in the general forum.