A working aircon pulls a surprising amount of water out of the air — several litres a day in Durban humidity. That condensate collects in a drip tray under the indoor coil and runs away through a drain line, usually to the outside wall. It is a gravity system with no pump on most domestic installations, which means it depends entirely on being clear and correctly fallen.
Why they block
The tray and drain stay permanently wet, and biological growth builds a slime that eventually plugs the outlet. Dust from the coil binds into it. On the coast, insects nest in the open end of the drain pipe outside. Once the outlet is blocked, the tray fills and overflows down the wall behind the unit — which is why the first sign is often a damp patch or peeling paint rather than visible dripping.
The other cause: bad falls
If the drain line was run flat or with a slight rise at some point, water sits in the sag instead of draining. This is an installation defect rather than a maintenance one, and no amount of flushing fixes it permanently. It needs re-routing.
The icing overlap
An indoor unit that suddenly drips heavily is often not a drain problem at all but a frozen coil melting, caused by blocked filters or low refrigerant. Diagnosing the difference matters, because flushing a drain will not stop a unit that is icing up.
Brands we fit and service
The condensate drain & drip tray market splits into hardware built for South African conditions and lookalikes that fail at the first hard season. These are the manufacturers we trust on our installations:
- Split
- midwall and cassette units; gravity and pumped drain installations
See our brand guides for how these manufacturers compare.
When the condensate drain & drip tray goes wrong
These are the failures we're called to most often — each with its symptoms, causes and our fix on the dedicated problems page:
- Water running down the wall under the indoor unit — A damp patch, peeling paint or visible water on the wall beneath the indoor unit, usually worst on humid days when the u…
Need this fixed or installed?
Our Aircon Service & Maintenance service covers condensate drain & drip tray work — from R700, quoted upfront and backed by our 12-month workmanship warranty.