Why Is My Aircon Leaking Water?

Leaks and drainage

Every aircon produces water when it cools. Warm, humid room air passes over the cold indoor coil, moisture condenses on it like water on a cold glass, and the drops run into a tray underneath. From there a drain pipe carries the water outside or into a drain. When any part of that path fails, the water comes out of the front of the unit instead.

Do this first: protect your walls and electrics

1. Switch the aircon off. Use the remote, then switch it off at the isolator or breaker, especially if water is running near a plug point, light switch or the unit's own wiring.
2. Catch the water. Put a bucket or towels underneath and move furniture, electronics and rugs out of the way.
3. Check the ceiling below. On upper floors, look for damp patches or sagging ceiling boards in the room below. If a ceiling is bulging with water or there is water near light fittings, keep the power to that circuit off and get help.
4. Leave it off until it's sorted. Running the unit keeps adding water to a system that can't drain it.

Where the water appears tells you a lot

What you see	Likely cause	Who should fix it
Drips or a steady trickle from the bottom or front of the indoor unit	Blocked drain line or full drain tray	You can check the outlet; clearing the line is a technician job
Water only after the unit has been running a while, sometimes with ice on the coil	Dirty filter or low refrigerant causing the coil to freeze and then thaw	Clean filters yourself; refrigerant checks need a technician
Water running down the wall along the pipes	Damaged pipe insulation sweating, or a drain pipe joint leaking	Technician
Water from a unit that has leaked since the day it was installed	Indoor unit or drain pipe not sloping correctly	Technician (installation correction)
Water at an indoor unit with a small pump, often on an inside wall	Condensate pump or its float switch has failed	Technician
Water dripping from the outdoor unit in heating mode	Normal condensation and defrost water	No action needed, unless it causes a slip hazard

Six reasons for an aircon leaking water

1. A blocked drain line

This is the most common cause by far. Dust that slips past the filters mixes with water in the tray and forms a slimy sludge that slowly narrows the drain pipe. Outside, the end of the pipe can be blocked by mud, insects, a wasp nest, plant growth or a pipe that has been pushed into a flower bed. The water backs up, the tray overflows and it drips from the unit.

2. A dirty filter freezing the coil

Clogged filters starve the coil of warm air, so it gets cold enough to freeze. When the unit cycles off or you switch it off, all that ice melts at once and overwhelms the tray. Low refrigerant causes the same freeze-and-thaw pattern. If you see ice, our guide to an aircon freezing up explains what to do next.

3. A cracked or misaligned drain tray

Trays can crack with age, or shift slightly if the unit was knocked or opened carelessly. A split tray leaks no matter how clean the drain is, and usually needs a replacement part.

4. Poor installation slope

Condensate drains by gravity, so the indoor unit should sit level or tilt very slightly towards the drain side, and the drain pipe needs a steady fall all the way out. A pipe that rises, sags or kinks along the wall traps water. If your unit has dripped on and off since installation, this is a strong suspect and needs the unit or pipework corrected.

5. A failed condensate pump

Where an indoor unit is on an inside wall, or the water has to go up before it can go out, a small pump lifts it away. These pumps can clog with sludge, or their float switch can stick, and then water overflows. A pump that runs non-stop, or one you no longer hear at all, is worth reporting to your technician.

6. Very humid days

Gauteng's summer thunderstorm season brings humid afternoons, and an aircon pulls far more water out of the air on those days. A drain that copes in dry weather can overflow when it's already half blocked. If you only find your aircon leaking water on muggy days, the drain is likely partly blocked rather than perfectly fine.

What you can safely check yourself

1. Clean the filters. With the unit off at the isolator, lift the front panel, slide out the filters, rinse them in lukewarm water and let them dry in the shade before refitting. See how to clean aircon filters for the full routine.
2. Find the drain outlet outside. Follow the thin plastic pipe from the unit to where it ends. Make sure it isn't buried in soil, crushed, or blocked by leaves or insects, and gently clear the tip if it is.
3. Look at the pipe run. Without pulling on anything, check whether the visible drain pipe dips or kinks on its way out.
4. Watch the outlet. Once the unit is running again, water should drip from the outlet within a while of cooling starting. No water there while the indoor unit drips means the blockage is further up.

When it's a job for a technician

Clearing a blocked line properly, replacing a tray or pump, re-levelling an indoor unit, re-insulating pipes and checking refrigerant all require opening the unit. A technician will flush the drain, clean the tray and coil, and confirm water flows freely before closing up. Regular aircon servicing includes flushing the drain, which prevents most of these leaks in the first place.

An aircon leaking water again after you've cleaned the filters needs proper attention before it stains walls or soaks a ceiling. Book a repair visit or call 0861 995 092, and we'll find where the water is going wrong through our aircon repair service. If the leak traces back to a poorly placed unit or a drain with no fall, our installation team can correct the setup. For water pouring near electrics after hours, emergency call-outs are available 24/7.