I have a little additional information, too: I have been washing the glass bottle drinkers in the dishwasher and they come out great -- spotless (top level) and clean. I am happiest overall with these bottles.
I put the smaller, plastic waterers in the DW, too (8 of them) and one of them started leaking along the seam afterwards
but, they did get very clean (no residue because of too narrow necks). I did have the plastic bottles on the bottom rack when the leak occurred but I moved them to the top and have not had a problem since. I do NOT put the plastic seals in the dishwasher or the corks because they could warp or crack.
Do you think where it's hot all the time there is more of a problem with waterers becoming homes for bacteria? I live where it's very moderate temperature wise, and I just wash with soap and water and use a bottle brush. I do this when i put new water in about every other day. I use tube waterers. I've only put bleach in the wash water a couple times a month because they aren't stinky or slimy. Though I have to say i have once in a while had a slimy or stinky one. Mostly with the parrots not the finches. I think If I had hundreds of birds I would be a lot more concerned with contamination.