Why is my air conditioner dripping water indoors?
An air conditioner dripping water inside almost always has a blocked drainage line. Producing water is a normal part of how the unit works, and when the line clogs with dust or algae that water overflows instead of draining away. It's a common fault, rarely a sign of serious damage, and usually resolved on the same visit.
Until a technician arrives, switch the unit off and isolate it at the mains. Water running near electrical components is an electrocution risk.
How to recognise it
- Dripping or running water from the indoor unit
- Damp patches on the wall below the unit
- The sound of water moving inside the casing
- A musty smell that grows stronger while running
Common causes
Blocked drainage line
Dust, algae and mould build up inside the pipe and close it off. This accounts for most cases, and the fix is to flush and clear the line.
Incorrect pipe fall
If the line wasn't installed on a downward gradient, gravity can't drain it and water pools until it overflows. This needs the pipework corrected.
A frozen evaporator thawing
When the evaporator freezes — usually from low refrigerant or a blocked filter — thawing produces more water than the drain tray can carry.
How we handle it
- 1Switching the unit off to stop the leak until we arrive
- 2Flushing and clearing the drainage line
- 3Checking the fall and re-running the pipe if needed
- 4Checking for ice on the evaporator, which points to a second fault
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