Guides The air conditioner is leaking water
The air conditioner is leaking water
Leaking water does not always mean a fault. Where the water appears makes the two cases easy to tell apart.
Updated 27 July 2026
Short answer
If the water runs through the wall, below the indoor unit, it is almost always the condensate pipe that is clogged or poorly angled: the water that the unit removes from the air has no way to escape and overflows the tray. This needs attention.
If the water drips of the outdoor unit, especially in winter with the unit heating up, it is normal: it's the defrost cycle draining, and there's nothing to do.
Why does an air conditioner produce condensation
When it cools down, the unit condenses moisture in the air, the same thing that happens to an ice-cold glass on a hot day. This water is collected in a tray inside the unit and leaves through a tube, the condensate drain, to the outside or to a drain.
On a humid day, a domestic unit can remove several litres of water per day. All this volume must have a path. When the path fails, water appears where it shouldn't.
Water inside: the condensate drain
This is the case that needs to be resolved. The usual causes:
Blocked drain pipe
Dust, slime and mold accumulate inside the tube and form a plug. Water backs up and overflows the front of the unit. It is the most common cause by far.
Wrong slope
The tube drains by gravity. If there is not enough drop, or if there is a belly in the middle where the water remains stagnant, it will not drain. It is an installation defect and cannot be corrected on its own.
Broken or misaligned drain tray
Less frequent, but happens on old units or after poorly reassembled cleaning.
Ice on the coil
When ice forms in the indoor unit (due to lack of refrigerant or very dirty filters), the ice melts at once when it is turned off and all the water comes out at the same time, far above what the tray can handle.
Water in the outdoor unit: normally normal
With the unit warming up, in winter, the outdoor unit forms ice and performs automatic defrosting cycles. During these cycles, water flows, sometimes a lot, and steam may come out. It is the expected operation.
With the unit cooling down, in summer, the outdoor unit should be practically dry. Water dripping from it at that point is worth a look.
What you can do and what you shouldn't
- You can wash the filters: if the clogging is just beginning, it sometimes resolves itself there.
- You can confirm that the tip of the tube, on the outside, is not covered, bent or placed in standing water.
- No blow or stick wires through the tube inside: the connection to the tray will be broken and the problem will be inside the wall.
- No cover the place where it drips. The water is still there, you just can't see it anymore.
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