Why is my AC leaking through the ceiling?
Usually a clogged condensate drain or an overflowing or rusted pan. The EPA advises keeping AC drip pans clean and drain lines unobstructed and flowing properly (EPA).
Isn't there supposed to be a backup?
Yes, where an overflow would damage the house. The International Residential Code requires an auxiliary or secondary drain for equipment where damage to building components could occur. Options include a separate pan with its own drain, a second drain line, or a water-level device that shuts the unit off (International Residential Code).
What should I do first?
Turn the system off at the thermostat so it stops making water, catch the drips and stay clear of any sagging section. An HVAC technician can clear the line and check the pan and float switch.
What has to be dried?
The attic insulation, the ceiling drywall and anything below. Wet insulation is discarded and replaced, and drywall is dried in place only if it has not swelled and the seams are intact (EPA). HVAC leaks are Category 1 water (Massachusetts DPH).
Common questions
Can I clear the AC drain line myself?
Many homeowners do with a wet vac at the outside end. If the pan is rusted or water keeps coming back, call a technician.
Why does my AC leak only in summer?
That is when it makes the most condensation, so a partial clog overflows.
Can an AC leak cause mold in the attic?
Yes, if insulation and wood stay wet. Dry or replace wet materials quickly.
Related guides
Sources
- EPA: A Brief Guide to Mold, Moisture and Your Home
- International Residential Code M1411.3: condensate disposal
- EPA: Mold Remediation in Schools and Commercial Buildings, Table 1
- Massachusetts DPH: quick reference, water damage response in buildings
Last reviewed November 13, 2026. This guide is general information, not legal, insurance or medical advice.