As with Gainer, I collect my ac run off water in the summer time. Here in the Washington DC area, there is lotsa humidity in da summah tahm!
I have three large stainless steel chemical tanks with lids and dump the run off into them--unless I am using the run off for my house plants.
I always filter the ac water before use; use it for mixing film developer and Photo Flo final rinse. I use filtered tap water for everything else. I have no chemical problems of which I am aware, but then I use no really esoteric chemistry: D23 and DK25R are very forgiving, dontcha know.
John, Mount Vernon, Virginia USA