Why isn't my AC drain pipe draining water?

An air conditioner drain pipe might stop flowing water due to several common issues. The most frequent cause is a physical blockage inside the PVC line resulting from an accumulation of algae, mold, dust, and slimy bacterial growth that restricts or completely stops the flow of condensation. Another potential reason is that the evaporator coil is frozen due to a dirty air filter or low refrigerant levels, temporarily halting water production until the ice melts. Additionally, a disconnected or broken drain pipe, a malfunctioning or burned-out condensate pump, or a clogged trap can prevent water from reaching or exiting the drain outlet properly. In rare cases during cool or dry weather, the air may lack humidity, meaning the system simply is not producing enough condensation to trigger visible drainage.