We were dispatched to the following : THERE IS A LEAK COMING FROM THE AC#18 NEAR 4124 THERE IS A BIG PUDDLE IN FRONT OF THE UNIT 4124 Brand : Carrier Model : FB4CNP060 Serial : 3016A87340 Tech Notes ; When I finally got in the unit to check on AC number 18, I noticed a pool of water running from the AC closet into the hallway. The unit was running but the condensate drain line was backed up and over pouring the safety cap. I also noticed that the air filter was sucked up into the coil and causing the unit to freeze. I could not find the outlet of the condensate drain on the outside of the building so there must be a larger drain that all the units dumped into? Solution : Therefore I used compressed air and blew they are through the condensate drain line and the water went down and cleared the back up. I remove the damage and wet filter from the coil and let it defrost. Also, I tilted the unit forward a slightly bit so that the water would flow towards the float switch