Window Air Conditioner Leaking Water Inside: 6 Causes and Fixes

The most common cause is an installation tilt problem. Window units are designed to sit tilted slightly downward toward the outside, typically about a quarter to half inch lower on the outdoor side, so condensation drains outward rather than pooling and dripping back into the room. If the unit is level or tilted the wrong way, water collects on the indoor side and leaks in.

Yes, this is normal and expected. Window units remove humidity from the room as part of the cooling process, and that moisture has to go somewhere. A properly installed unit drains this condensation out the back or bottom to the outside; the problem is only when water appears inside the room, not outside.

A clogged filter restricts airflow across the evaporator coil, which can cause the coil to get too cold and ice over. When that ice later melts, usually when the compressor cycles off or the unit is turned off, it can produce more water than the drain system is designed to handle at once, leading to an overflow inside.

It's worth turning it off and checking the installation tilt and drain before continuing to run it, especially if water is reaching a windowsill, wall, or flooring that could be damaged. Most leaks are a straightforward installation or maintenance fix, not a sign the unit needs replacement.