AC leaking water inside the house

Symptoms

• Water dripping or pooling near the indoor air handler
• Water stains on the ceiling below an attic-mounted unit
• May be accompanied by a musty smell

Likely causes

• CommonClogged condensate drain lineAlgae and sediment naturally build up in the drain line and can block it over time.
• CommonFull or overflowing condensate drain panA backed-up line causes the pan to overflow onto the floor or ceiling below.
• PossibleCracked or rusted drain panAn older metal pan can rust through, or a plastic one can crack, and leak even with clear drainage.
• PossibleFrozen coil that has thawed and produced excess waterMore water than the drain can handle at once may overflow, especially if the line is already partly restricted.
• PossibleFailed condensate pump (if used, common in basements)If the unit relies on a pump to move water uphill to a drain, a failed pump lets water back up.

What to do

1. Turn off the AC to stop adding more water while you investigate.
2. Locate the condensate drain line, usually PVC pipe running from the indoor unit to a floor drain or outside.
3. Check for a clog by looking at the line's exit point for slow or no dripping when the system had been running.
4. Use a wet/dry shop vac at the outside termination point to suck out any blockage, or flush the line with water and a little vinegar from the indoor access point.
5. Check the drain pan for visible cracks or rust holes if you can access it.
6. If there's a condensate pump, check that its float switch moves freely and the pump runs when water is added to the reservoir.
7. Turn the AC back on and monitor for continued leaking before leaving it unattended.

Tools and parts

• Wet/dry shop vac
• White vinegar
• Bucket

When to call a pro

Call an HVAC technician if the drain line clears but leaking continues, or if the drain pan itself is cracked and needs replacement.

Safety