Shut cooling or condensing heat off when water approaches wiring. The source may be a blocked drain, pump, frozen coil, humidifier or plumbing. Look at the exposed drain tube and trap for water that does not move. Look at the pump reservoir and whether the pump starts when the water is high.
What this covers
- Residential furnaces, air handlers and heat pumps with visible condensate drainage
What it does not cover
Differential
Likely causes of “Water is collecting around the furnace or air handler”, and how to tell them apart
- 1
The condensate drain is blocked or the trap is full
What separates it Water pools under a high-efficiency furnace or an air handler after a run of cooling or heating, and the drain tube is clogged or the trap is full of slime.
How to confirm Look at the exposed drain tube and trap for water that does not move.
- 2
The condensate pump has failed or its reservoir is full
What separates it Water collects around the pump, and the float in the reservoir is stuck or the pump does not run.
How to confirm Look at the pump reservoir and whether the pump starts when the water is high.
- 3
The evaporator coil froze and is now melting
What separates it Ice appeared on the indoor coil or the refrigerant line, and the water arrives once the ice melts.
How to confirm Turn off cooling and let the coil thaw, then check the filter and airflow.
- 4
A humidifier or a plumbing leak is the source
What separates it Water appears in the same place even when the system is off, and a humidifier's water line or a nearby pipe is wet.
How to confirm Look at the humidifier and the nearby pipes for the first wet spot.
Before you touch a setting
Record this first — changing settings destroys the evidence
- Where the first drip is, and whether the system was heating or cooling at the time.
- The state of the drain line, the trap, the pump and the pan.
- Whether ice is visible on the coil or the refrigerant line.
Try in this order
0 of 4 completedCapture the exact state
ReversibleDry the area safely and locate the first drip while noting the operating mode.
Separate the likely fault domains
ReversibleInspect only exposed drain tubing, trap, pump reservoir and external pan.
Correct only the proven, accessible condition
ReversibleClear a customer-serviceable drain by the manufacturer method or arrange HVAC/plumbing service.
Verify once before going farther
ReversibleRun the prior mode and confirm drainage without new water.
Stop boundary
When this stops being a self-service repair
- !Turn off cooling or the furnace and the power to the unit if water is near wiring, and mop the area before it spreads.
- !Have an HVAC technician or a plumber clear a hidden or stubborn drain.
Evidence ledger
Sources behind this answer
Exact questions
Common questions
Where does furnace condensate come from?+
A high-efficiency furnace cools its exhaust until water vapour condenses, and that water drains away through a small tube. An air conditioner's coil also produces water in the same way.
Why is water around my furnace?+
Condensate from a high-efficiency furnace or an air handler may be backing up because of a blocked drain or a failed pump.
Can water damage the furnace?+
Yes. It can damage controls and cause rust, so fix it quickly.