Why is my aircon leaking water? Causes, quick fixes and repair costs

Turn the unit off before you investigate. Water tracking down a wall can reach the electrical terminals and the control board, turning a $90 drainage clean into a board replacement.

Condensate drains by gravity through a narrow pipe. Over months, dust plus biological slime forms a plug, water backs up in the drain pan, and it overflows out of the front of the unit.

A technician clears this with a vacuum pump or nitrogen flush, then treats the line. It is a routine job, not a major repair.

When the fins are coated in grime, condensate no longer runs down cleanly into the pan — it clings, forms droplets, and gets blown out into the room by the fan. Chemical washing restores the surface so water sheds properly.

Ice that builds up during operation melts faster than the pan can drain once the unit stops, and it overflows. If you see leaking together with ice, treat the freezing as the real fault — usually airflow restriction or low refrigerant.

The drain must fall continuously towards the discharge point. Units mounted slightly off-level, or drain lines that sag behind a false ceiling, hold water and eventually back up.

This is a workmanship fault. If your unit has leaked since day one, it was installed wrong.

Plastic pans crack with age and UV exposure, and drain hoses work loose from the pan spigot during servicing. Both produce a steady drip from a fixed point rather than an overflow across the front.

If the drip is coming from the copper pipes rather than the unit body, the insulation lagging has degraded and cold pipe is condensing room humidity. Re-lagging is inexpensive.

Household drain cleaners damage the pan and the pipe joints. A proper flush uses a vacuum from the discharge end.

• Safe: switch off, mop up, remove and wash the filters, check the outdoor drain outlet is actually dripping
• Safe: clear obvious debris from the drain outlet point
• Not safe: pouring chemicals down the drain line, dismantling the indoor casing, poking wire into the pipe

Drainage clearing is usually done during a chemical wash from $90 per unit, which also addresses the coil that caused the blockage in the first place. Standalone drainage pipe repairs are quoted after inspection.

Most leak jobs are completed in a single visit.