This is the most common cause of a leaking aircond, full stop. As your aircond cools the air, it pulls moisture out of it — that moisture collects in a drain pan and flows out through a small pipe (the condensate drain line). Over time, this pipe gets clogged with algae, mould, dust, and grime, especially in Malaysia's humid climate.
When the drain line is blocked, water backs up into the drain pan and eventually overflows — usually showing up as a drip or stream from the bottom of your indoor unit, or water stains on the ceiling below it.
How to tell: The dripping is slow and steady, often worse in humid weather. You may notice a musty smell coming from the unit at the same time.
A dirty filter restricts airflow across the evaporator coil. When airflow is too low, the coil gets too cold and freezes over — you'll sometimes see ice forming on the indoor unit. When the unit is turned off (or the temperature rises), that ice melts all at once, producing far more water than the drain pan can handle.
How to tell: The leak is worse after the unit has been running for a few hours. You may see ice or frost on the indoor unit while it's running, and the room isn't cooling as well as usual.
Refrigerant is the gas that actually does the cooling. If your unit has a refrigerant leak, the pressure in the system drops and the evaporator coil gets abnormally cold — causing it to ice up, just like the filter problem above. When it melts, you get a water leak.
This is different from the filter issue because it will keep happening no matter how often you clean the filter, and you'll notice your room isn't getting cool even when the unit runs for a long time.
How to tell: The unit blows air but the room never gets cold. Ice forms on the coil or even on the refrigerant piping outside. You may hear a faint hissing sound near the unit.
The drain pan sits under the evaporator coil to catch condensation. Over years of use, plastic drain pans can crack, warp, or develop leaks at the seams. This is more common in units that are 5–8 years old or units that have had blocked drain lines (because standing water accelerates wear on the pan).
How to tell: The drain line is clear and flowing freely, but water is still leaking from the unit. A technician can visually inspect the pan during servicing.
For the condensate to drain properly, the indoor unit needs to be installed at a very slight angle — tilted just enough for water to flow toward the drain outlet. If the unit is perfectly level (or tilted the wrong way), water pools in the drain pan instead of draining, and eventually spills over.
This is usually a problem with newer installations done by inexperienced contractors, or in older installations where the wall has shifted slightly over the years.
How to tell: The problem started shortly after installation or has gradually worsened. Water tends to drip from one specific corner of the unit rather than the drain outlet.
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WhatsApp for Free DiagnosisCan I Fix a Leaking Aircond Myself?
In two cases — a dirty filter and a clogged drain line — there are things you can do yourself as a first step. Cleaning your filter is straightforward: remove it, rinse under running water, let it dry, and reinsert it. Some homeowners also flush their drain line with a cup of diluted bleach poured into the drain pan.
However, anything involving the evaporator coil, refrigerant, drain pan replacement, or remounting the unit should be handled by a professional. Attempting these without experience risks damaging the unit, voiding the warranty, or — in the case of refrigerant — causing harm.
As a rule of thumb: if cleaning the filter and waiting 24 hours doesn't stop the leak, it's time to call a technician.
How to Prevent Aircond Leaks
The vast majority of aircond leaks are preventable with regular servicing. Here's what a routine service covers that directly prevents leaks:
- Filter cleaning — prevents airflow restriction and coil icing
- Drain line flushing — clears blockages before they cause overflow
- Coil inspection — checks for ice buildup, dirt, or signs of refrigerant loss
- Drain pan inspection — catches cracks early before they become water damage
In Malaysia's climate, we recommend servicing your aircond every 3–4 months for home units and every 1–2 months for commercial units with heavy usage. A unit that's regularly serviced is far less likely to develop a leak — and if one does develop, it'll be caught early before causing water damage to your walls or ceiling.
Quick Summary: 5 Causes of a Leaking Aircond
- Clogged drain line — most common; clear it during a service visit
- Dirty air filter — restricts airflow, freezes coil; clean filter every 3–4 months
- Low refrigerant — causes coil to ice up; needs professional repair + gas top-up
- Cracked drain pan — usually 5+ year old units; needs replacement
- Incorrect installation angle — water pools and overflows; needs remounting