Adding bleach to a toilet with a 'drop in'

I recently asked my plumber about using those drop-ins, and he suggested not using them.  The reason I asked, is that I noticed a lot of residue at the bottom of the tank from them not fully dissolving over time.  It was gunking stuff up a bit.  He said a better idea is to buy the large chlorine tablets they sell at Pool supply stores - put it in a ziplock and smash it into some pieces, and just put one piece of it in the toilet.  Alot cheaper than to keep buying dropins too.

I was always taught to never mix bleach with anything that has ammonia in it - something about it turning into chlorine-gas and killing everyone in the neighborhood.. although my mother probably exaggerated a bit, you probably get the idea.

Read the label to make sure your DropIns dont have any ammonia - if they dont it's probably safe, unless there is some other danger i'm not aware of.

If in doubt, consult with a chemist.. or meth-cook.

by safe do you mean there wont be an explosion? (youre not drinking the water right?)and isnt there bleach already in some drop ins? i think it should be ok. it may just not give you the blue color anymore. are you putting it in the tank or just the bowl? extra clean freak huh? =)