I have an old air conditioner and furnace... Just the other day I noticed a bunch of water on the floor and it is leaking from between the duct work and the top of the furnace. I removed the drain hose and flushed it out with bleach, seems to have no obstructions so I hooked it back up to the 1/2" copper fitting that runs to a drain. It does go uphill at the end but it has never given me this problem in the last 3 years so I doubt that is it. What is the next step? Could it need a new evaporator coil? Could it just be plugged up somewhere else? Thanks, this is driving me nuts and I am almost ready to get a a plumber in to look at it.