What a Furnace Condensate Pump Does

High-efficiency furnaces and air conditioners make water. If the cabinet sits in a closet or an attic with no drain below it, that water cannot run downhill. A condensate pump collects it in a small tank and pushes it through a plastic tube to a laundry drain, a standpipe, or a stub outside. You hear a short buzz every so often while the system runs. That buzz is normal.

When it is not normal

• The pump runs constantly and the tank never drops.
• The pump never runs and the tank is full.
• Water is on the floor and the furnace or air conditioner will not start.
• The discharge tube is kinked, frozen at an outside wall, or popped off the barb.

The safety float exists so a dead pump does not become a flood. The equipment stops on purpose. Jumping that switch out restores heat until the closet is soaked. Do not do that. Also do not open the pump and hot-wire the motor.

What a repair actually is

Sometimes the tube is plugged with algae and the pump is fine. Sometimes the impeller is jammed or the motor is done. The inlet from the furnace trap can be plugged while the pump itself is innocent, which looks the same from the floor. A technician clears the trap, the pump, and the discharge, then confirms the safety switch opens when the tank is lifted. Pouring bleach into the reservoir attacks the seals and does not thaw a frozen outdoor discharge.

No heat plus a full pump is heating repair. Water at the air conditioner pan is the cooling version of the same part, covered with AC water leaks.

Common questions