Why ACs leak water
- Clogged condensate line: algae and debris block the drain.
- Rusted or cracked drain pan on older systems.
- Frozen coil melting faster than the pan can drain (see frozen AC).
- Failed condensate pump in basements and attics without gravity drains.
- Tripped float switch: many systems shut off cooling when the pan is full, which is a clue rather than a fault.
Clearing a drain line
- Turn the system off at the thermostat and at the service switch.
- Find the drain access (often a T-shaped fitting with a cap near the indoor unit).
- Use a wet/dry vacuum on the outdoor end of the line to pull the clog out.
- Flush with a cup of water to confirm it drains. Some manufacturers recommend a mild vinegar flush; check your manual first.
Prevention
Annual maintenance should include clearing and testing the condensate line and float switch. If your air handler is in an attic, make sure there is a secondary pan or float switch to protect the ceiling.
