How Aircon Leaks Cause Mould in Singapore Homes (And What to Do About It)

Mould showing up around your aircon unit is more common than most homeowners realise. In many cases, the cause isn’t poor cleaning habits or lack of ventilation. It’s hidden water leakage from the unit itself. Even after wiping it away or repainting, mould often returns unless the root cause is fixed.

Let’s break down what’s really happening and how to stop it for good.

Why Mould Often Appears Near the Aircon

When an aircon unit is running, it produces condensation. Ideally, that moisture is drained away through proper piping. But if the drainage pipe is blocked, the unit is tilted incorrectly, or insulation fails, that water can leak out and soak the surrounding wall or internal surfaces.

In Singapore’s humid climate, even small amounts of trapped moisture can create the perfect environment for mould growth.

Common Signs the Mould Is Aircon-Related

• Mould appears just below or around the aircon unit. 

• Paint or wallpaper starts peeling or bubbling due to aircon leakage.

• The wall feels damp or looks discoloured.

• You see water streaks or marks on the wall or surface near the aircon.

• The mould keeps coming back even after cleaning.

These are usually signs that the issue isn’t just on the surface. The water source is active and feeding mould from behind or beneath the material.

What We Typically See on the Job

In many homes, we find that mould near the aircon unit is just the visible part of a deeper issue. Once we start inspecting the area, we often come across:

 • Moisture trapped in the wall behind or beneath the aircon.

 • Mould spreading outward from a hidden leak point.

 • Homeowners who had already tried vinegar or repainted the wall, only for the mould to return worse than before.

Often, people don’t even realise there’s a leak until the area becomes visibly stained or the mould becomes hard to ignore.

Why DIY Cleaning Doesn’t Work in These Cases

Surface cleaners like vinegar can only do so much. If the mould is caused by a hidden leak, wiping the outside does nothing to stop spores growing underneath.

The affected surface is usually porous. Paint, drywall, or plaster holds moisture. Once water gets inside, it becomes a breeding ground for hidden mould that slowly pushes back to the surface.

What to Do If You Suspect an Aircon Leak

Here’s the proper order of action if you suspect your mould problem is aircon-related:

1. Get a certified aircon technician to check for leaks, clogs, or poor drainage

2. Once repaired, contact a mould remediation team to inspect and treat the affected zone

3. Avoid repainting until the leak is confirmed resolved and the area has been decontaminated

4. Improve ventilation and monitor moisture levels to prevent a repeat

At Sterng, we often come in after aircon repairs to fully treat and neutralise the area. That way, the mould doesn’t return.

How We Treat Mould Around Aircon Units

• We apply an alkaline-based solution to kill spores at the root 

• Follow up with fogging to neutralise airborne spores in the room 

• Provide guidance on how to reduce future moisture build-up near the unit

The goal is not just to clean what’s visible. It’s to change the environment so mould cannot grow back.

Final Thoughts

Mould around your aircon might seem like a surface issue, but it usually isn’t. It’s a sign of excess moisture, often caused by leaks. In Singapore’s climate, ignoring it will only make it worse.

If you’ve spotted mould forming around your aircon, Sterng offers free inspections across Singapore. Tap here to WhatsApp us and we’ll help you get ahead of it before it spreads.