Condensate Backups Continued

Leaks & Overflows

The wet, warm environment of a condensate collector beneath a central air conditioner evaporator coil is a perfect algae breeding ground. This biological growth may migrate into the condensate drain line or the drain trap and form a blockage. Condensate overflow due to a blocked drain may be caught by an overflow pan beneath the air handler, but if the overflow pan is missing, or has cracked or developed a hole, or if the overflow pan’s drain line is plumbed to the same primary drain line that is clogged, water leakage will ensue. Property damage from unseen condensate leakage can be extensive and expensive by the time a leak is finally noted by occupants.

Drain Trap

A central air system routes condensation through a U-shaped trap located in the drain line just outside the air handler. It’s similar to the trap under your kitchen or bathroom sink; water in the trap prevents sewer gases originating where the condensate drain pipe terminates from infiltrating the air handler. In some conditions, such as during a long season of non-operation or when a gravity-fed drain line is not installed with the proper incline, the condensate drain trap may dry out and allow sewer gases to pass through the line. Unexplained noxious odors emitted from air conditioner supply vents in the home are the primary symptom of a dry condensate drain trap.

System Shutdown

Because of the potential of severe property damage from unseen leaks, many condensate drain systems incorporate an overflow sensor. When a clogged condensate drain causes a backup that reaches overflow stage, the sensor cuts off power to the system. The coil and collector are sealed inside the air handler and generally not accessible for a do-it-yourself project. Until an HVAC technician can arrive to open the air handler, unblock the drain line, and clear the pan, the air conditioner will be unusable.