Why does a clogged AC drain line stain the ceiling?
The air handler produces water as it cools, and the drain line carries it away. When the line clogs, water fills the pan and spills over, soaking the insulation and drywall under the unit. In Texas homes with the air handler in the attic, that is a common reason for a ceiling stain.
The leak is easy to miss. Water seeps into the insulation first, which hides it, and only appears on the ceiling once the drywall has absorbed more than it can hold. By then the area above can be much larger than the stain.
A float switch can shut off the AC when the pan fills, and a secondary drain pan with its own line can carry overflow to a visible spot. Ask an A/C contractor what your system has.
What should you do when you see an AC leak?
Turn the AC off at the thermostat, since a running system keeps producing water. Stay out from under a wet or bulging ceiling, move belongings and photograph the stain. Call an A/C contractor for the line or pan, and call the drying crew for the ceiling and insulation.
A shop vacuum on the drain line's outlet can clear some clogs, but do not climb into an attic with standing water near wiring or in extreme heat. Attics get dangerously hot in summer, and the work is better done early in the morning or by a professional.
Photograph the stain, the pan and any wet insulation before anything is moved, since your insurer may want to see them.
Does homeowners insurance cover an AC condensate leak?
Coverage depends on your policy and on how the leak is described. A standard homeowners policy often covers sudden and accidental water damage but usually not a long-term leak, which condensate overflow can be. Your insurer decides, so call early, keep photos and ask your agent about your wording.
The crew can give you moisture readings and photos for your claim. It cannot negotiate the claim or cover your deductible, and Texas law keeps contractors out of the adjuster's role.
The Texas Department of Insurance offers consumer help with claims.
Can a slow AC leak cause mold?
Yes. A condensate leak runs for days or weeks before it shows, so insulation, ceiling drywall and framing may stay damp long enough for mold to start. The EPA's 24 to 48 hours is a drying guideline, not a deadline, and mold can be present even if materials were dried within it.
If mold is found, Texas licenses mold assessors and mold remediators separately, and a job at or above 25 contiguous square feet generally needs both, from two different license holders. The drying crew does not offer testing and removal as one service.
The mold inspection and mold remediation pages explain each role.
How can you keep a condensate line from clogging again?
Have an A/C contractor clear the line and check the pan and float switch, and repeat that check each cooling season. Clogs come from algae and sludge, so regular flushing helps. It is maintenance, not a guarantee, and a contractor can tell you what suits your system.
Some owners ask about treatment tablets or a periodic vinegar flush, which is a question for the contractor, since the wrong product can harm the equipment.
Check the pan and the ceiling under the unit each spring, before the heat arrives. A small stain found in May is far cheaper than a wet ceiling found in August.
