Locating the Source of the Leak

Double A Plumbing removed drywall to inspect drains and discovered that the source of the leak was a cracked condensate drain pipe. The pipe was apparently cracked when the duct for the room vent was installed, either at the time of installation, or from the pressure that was put on the pipe, which made it vulnerable to cracking during cold, winter temperatures.

Photos below show the drains roughed in vertical, the installation of the vent and duct, the pipe bent to the left beside the duct, and the leak.