Water dripping from your wall unit is one of the most alarming things that can happen when you're sitting at home. It looks serious. It feels urgent. It makes you think something expensive is broken.
In most cases, it isn't.
Aircon water leaks are one of the most common home maintenance issues in Singapore — and the majority of them have a simple, fixable cause. This article explains exactly what's happening inside your unit, why water appears in the first place, and what you can do about it before calling anyone.
First: Why Does Your Aircon Produce Water at All?
This surprises people who haven't thought about it before. Your aircon doesn't just blow cold air — it actively pulls moisture out of the air in your room.
Here's how: the indoor unit contains a very cold metal coil (the evaporator coil). When warm, humid Singapore air is drawn over that coil, the moisture in the air condenses on the surface — exactly like water droplets forming on a cold glass of Milo.
That condensed water has to go somewhere. Under normal operation, it drips into a water tray (also called the drip pan or condensate tray) directly below the coil, and then flows out of your home through a drain pipe — usually into a bathroom wall cavity or externally.
When everything is working correctly, you never see or feel any of this water — it quietly drains away. A leak means something in this system has broken down. Here are the four most common reasons why.
Cause #1: Blocked Drain Pipe (Most Common)
This is the cause behind the majority of aircon leaks in Singapore homes.
Over time, algae, dust, and mould build up inside the drain pipe. The pipe narrows, slows, and eventually blocks completely. Water backs up into the tray, the tray overflows, and water spills out of the unit — usually dripping from the front edge or the sides.
How to fix it yourself:
- Locate the drain pipe outlet — usually in your bathroom wall or near an external drain
- Use a wet/dry vacuum to suction from the outlet end for 30 seconds (clears most blockages instantly)
- Alternatively, pour a cup of diluted bleach (1:10 ratio with water) into the drain access point on the indoor unit — this kills the algae causing the blockage
- Run the aircon and check if water is flowing out normally again
This fix takes under 15 minutes and costs nothing if you already have a vacuum.
Cause #2: Dirty or Frozen Evaporator Coil
When the evaporator coil is heavily coated in dust and grime, airflow over the coil drops. The coil gets colder than it should — cold enough for the condensation on its surface to freeze rather than drip into the tray.
You now have ice forming inside your aircon unit.
When the unit cycles off, or when you finally notice the aircon isn't cold and turn it off, that ice melts rapidly — producing far more water than the tray can handle. The result is a sudden, heavy drip or pour of water from the unit.
Signs this is your problem: the aircon is not very cold even on high setting, and the leak is sudden and heavy rather than a slow drip.
Quick fix: Turn the aircon off and switch the fan to "fan only" mode for 30–60 minutes. This lets the ice melt slowly into the tray and drain. Do not pry at the ice — you can damage the coil fins. Once melted, clean the air filter (the mesh panel behind the front cover) — a clogged filter is often the root cause of reduced airflow.
Cause #3: Dirty or Overflowing Water Tray
Even if the drain pipe is clear, the water tray itself accumulates sludge over time. In humid Singapore, mould and algae grow in standing water quickly. The tray can crack, corrode, or simply fill up with biological gunk that reduces its capacity.
Signs: a musty smell accompanying the drip, or visible brown/black residue on the tray if you remove the front panel cover.
Quick fix: Remove the tray if your unit allows it (some slide out), scrub with diluted bleach solution, rinse thoroughly, and reinstall. If the tray is cracked, it needs replacement — this is a cheap part that any aircon technician carries.
Cause #4: Low Refrigerant (Gas Leak)
Less common, but worth knowing. If your system has a slow refrigerant (gas) leak, the pressure drop causes the evaporator coil to get abnormally cold — leading to the same ice-formation problem described in Cause #2.
The difference: cleaning the filter won't fix it this time. The unit will ice up again relatively quickly after you defrost it.
Signs: aircon is consistently not cold on any setting, and the leak comes back within days of defrosting. You may also hear a faint hissing near the indoor unit or notice ice visible through the vents.
This one requires a licensed technician. Refrigerant top-ups must be done by a certified professional — it's both a technical requirement and a legal one in Singapore. The technician also needs to locate and seal the source of the leak, or the refrigerant will just deplete again.
Quick Diagnosis Guide
| Symptom | Most Likely Cause |
|---|---|
| Slow, steady drip from front edge | Blocked drain pipe |
| Sudden heavy pour when turned off | Frozen coil — ice melting |
| Musty smell with the drip | Dirty/mouldy water tray |
| Not cold + keeps icing up | Low refrigerant (gas leak) |
| Drip after recent installation | Incorrect pipe slope or loose connection |
When to Call Someone
You can fix the first three causes yourself in under an hour with basic household tools. Call a technician when:
- The unit re-ices within a few days of defrosting (refrigerant leak)
- The tray is visibly cracked or corroded and needs replacement
- You've cleared the drain and it blocks again within weeks (sign of deeper pipe damage)
- There's water damage to the wall or ceiling behind the unit
Most water leaks in Singapore aircon units are a blocked drain pipe. Check that first — you'll solve it 70% of the time without spending a dollar.
If you've worked through this guide and still can't find the cause, Scout connects you directly with skilled, independent aircon technicians — no agency markup. Find one near you.