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Water leaking at the indoor unit: guided troubleshooting

Water in the pan, on the floor or through the ceiling under the air handler or furnace coil. Answer each question from what you see on site.

Step 1

Is the indoor coil or suction line iced up?

For trained technicians. Line voltage, gas and refrigerant work can injure or kill. Never jumper a safety switch to keep equipment running, and follow the manufacturer's instructions for the unit in front of you.
See every step in this flow
  1. Is the indoor coil or suction line iced up?
    • Yes: Frozen coil
    • No: Is the primary drain pan full of standing water?
  2. Is the primary drain pan full of standing water?
    • Yes: Does the drain line clear when you vacuum or flush it?
    • No, the pan is dry or draining: Where is the water coming from?
  3. Does the drain line clear when you vacuum or flush it?
    • Yes, it was clogged: Clogged drain
    • No, it still won't drain: Drain layout
  4. Where is the water coming from?
    • Blowing off the coil into the duct or cabinet: Water blowing off the coil
    • A cracked or rusted pan: Failed drain pan
    • Sweating duct or suction line: Condensation on ducts or lines
    • The condensate pump: Condensate pump

Where each path ends

Frozen coil

The water is ice melting past the pan. Thaw it with the blower, then find out why it froze: airflow first, charge second.

Clogged drain

Clear the trap and line, then check that a float switch is installed and wired to shut the system off next time.

Drain layout

Check the slope, the trap and the vent. On a negative-pressure coil a missing or dry trap lets the blower hold water in the pan.

Water blowing off the coil

Usually too much airflow across a wet coil, or a dirty coil that sheets water unevenly. Check blower speed and coil condition.

Failed drain pan

A cracked plastic pan or a rusted-through metal one has to be replaced; sealants don't last. Add a secondary pan and float switch where the unit is over a ceiling.

Condensation on ducts or lines

Missing or wet insulation, or very high indoor humidity. Insulate the suction line and duct, and check why the house is humid.

Condensate pump

Check that the pump has power, the float moves freely, the check valve isn't stuck and the discharge tube isn't kinked or clogged. Wire its safety switch to stop the system if it fails.