air conditioning drain

senerio: two story condo building. upper and lower unit's a/c drains merge into one line and then discharge to the outside. drain gets plugged outside and water backs up into lower unit. this happened in florida and lots of water was generated. any thoughts on building codes, poor design etc.

Where does it drain to: obviously the drain should terminate above grade to keep out dirt, bugs, grass clippings, etc.

Yep, I understand. I live in Florida too. Everytime I change the filter(s) in my upstairs and downstairs unit(s) I pour a cup of bleach down the a/c drain.

I hope that's what you are talking about. You get a buildup inside the pipe. If you can't clear it, just blow into the pipe with all openings covered except the exit end.