The defrost drain tube, also known as the drain tube or condensate drain tube, is a small tube that carries water from the evaporator coils to the drip pan located at the bottom of the fridge. Its primary function is to drain the condensate water that forms during the defrost cycle, which occurs when the fridge's automatic defrost system kicks in to remove frost and ice buildup on the evaporator coils.
In an automatic defrost refrigerator, the evaporator coils inside the freezer compartment get cold enough to freeze moisture from the air. Every 8 to 12 hours, a defrost heater melts this frost. The resulting water collects in a trough and flows through the to a drain pan (drip pan) located near the compressor at the bottom of the unit. The heat generated by the compressor then evaporates the water back into the air. Signs of a Clogged Defrost Drain Tube defrost drain tube