Why is my aircon leaking water inside?
Water dripping indoors is stressful, and it usually traces to one of three paths: a blocked drain, a freezing coil, or sagging piping. A steady drip points to the drain, sudden bursts point to a freezing coil, and a drip that moves points to the piping.
By Team Snowflake | Reviewed 30 May 2026
1. Drain-path blockage
If cooling still feels mostly normal but water drips steadily from one fixed point, the drain path is usually backing up. Dust and mineral residue collect in the tray or pipe until water queues inside the unit and spills over the tray lip. If you are not sure whether the water points to drainage, icing, buildup, or trunking, use the aircon water leak checker before choosing the service.
How to tell
This path is a steady fixed drip while the unit runs. Unlike freeze-thaw, it does not arrive in bursts after shutdown. Unlike slope faults, the drip point does not move along the trunking. Normal cooling plus one leak point starts with drainage.
- Steady drip pattern during runtime.
- Gurgling water sound near the indoor unit.
- Cooling can still feel acceptable at first.
- Drip always from the same fixed point on the casing.
How we confirm it
We clear and flush the drainage path, correct slope or insulation issues where needed, and retest under cooling load to confirm leaking stops.
Avoid gas work before drain behaviour is checked. A pure drain obstruction will not be fixed by refrigerant work.
2. Freeze-thaw cycle
If the leak comes in bursts after weaker cooling or after shutdown, the coil is usually freezing during the run and dumping meltwater when the ice releases. Low airflow or low refrigerant can push the coil below freezing. What looks like a drain problem from the room is often a freeze-thaw cycle instead.
How to tell
This path arrives in bursts. Unlike a blocked drain, it is heavy after weaker cooling or shutdown. Unlike slope faults, the trigger is thermal, not routing. Ice or frost on the copper pipe points to freeze-up.
- Leak appears in bursts, not a constant flow.
- Cooling weakens before leakage worsens.
- Ice beads form on the copper pipe, or white frost crystals appear on the line set.
How we confirm it
We remove the root restriction causing freeze-up, restore airflow or refrigerant balance as needed, and retest for stable operation without icing.
Avoid treating every indoor leak as a drain issue before airflow, coil icing, and refrigerant condition are checked.
3. Condensation routing or slope issue
If moisture shows up at different points along the trunking or wall, the issue is usually slope, routing, or insulation rather than a simple tray blockage. Water pools in a dip or forms condensation on an exposed cold section. The leak point then shifts instead of staying fixed.
How to tell
This path moves along the route. Unlike a blocked drain, the drip point shifts instead of staying fixed. Unlike freeze-thaw, it follows slope, dips, or exposed cold pipe rather than thermal bursts. The water follows the lowest path through poor routing.
- Drip location shifts along trunking or wall path.
- Leak timing changes with weather or runtime.
- Moisture appears even when cooling output seems normal.
How we confirm it
We trace the full water path, correct slope, re-route or re-insulate the affected section, and retest under cooling load to confirm leaking stops.
A full evaporator coil replacement or complete re-piping will not fix a slope problem. The leak returns after each humid period until the piping is re-routed or the slope is corrected. Confirm the water path and route before recommending major parts work.
Useful next steps
Related reading
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