AC leaking water inside the house

Water around the indoor unit usually comes from a clogged condensate drain line, a dirty filter, or ice melting off the coil. Most drain clogs clear with a wet/dry vac and vinegar. Five questions point you to the right fix.

Also searched as: ac leaking water, why is my ac leaking water, ac condensate drain line clogged, water around furnace when ac is on.

Before you start. Turn the AC off at the thermostat before you work on the drain. If water reaches a light fixture or outlet, stay clear of it, and switch off that breaker only if you can reach the panel with dry hands while standing on a dry floor.

A wet/dry vacuum hose held against the end of a condensate drain pipe outside a house

Every question and answer on this page, in order

Question 1: Where is the water?

The indoor unit is the furnace or air handler, usually in a closet, basement, attic or garage.

At the indoor unit, the furnace, or in the drain pan: go to question 2
Somewhere else: a ceiling, a wall, or only outside: The source isn't clear: call an HVAC technician

Question 2: Do you see ice on the copper line or the indoor unit?

Yes, there's ice or frost: Likely cause: ice melting off the coil
No ice: go to question 3

Question 3: Have you cleared this drain before, only for it to clog again, or is there water damage?

Water damage means stained ceilings or drywall, warped flooring, or a rusted-through drain pan.

Yes, it keeps coming back, or there's damage: Recurring clog or water damage: call an HVAC technician
No, this is the first time: go to question 4

Question 4: Has the AC been shutting off on its own, or do you notice a musty smell or a muggy house?

Lennox lists musty smells and higher humidity as signs of a clogged drain line. Many systems also have a float switch that shuts the AC off when the pan fills.

Yes, one or more of those: Likely cause: a clogged condensate drain line
No, just the water: go to question 5

Question 5: How does the air filter look?

Slide the filter out and hold it up to a light.

Gray or dusty, and little light comes through: Likely cause: a dirty filter and coil
Clean, or changed in the last month: Likely cause: a clogged condensate drain line

Possible results

Need the words for the phone call? Build a what-to-tell-the-technician checklist, or read when to call an hvac pro.