Why Your Aircon Drips Inside the Room: Drainage, Ice and the Fixes That Last

Aircon water leaking into the room almost always comes down to two things: a blocked or slanted condensate drain, or ice that formed on the cooling coil and then melted faster than the tray can handle. In Singapore's humid climate, a fan coil pulls a surprising amount of moisture out of the air, and every drop has to reach the drain pipe. When that path is choked with algae, dust and slime, the water backs up and finds the easiest way out, which is your wall or floor.

The second cause, ice, usually points to low refrigerant or a dirty filter starving the coil of airflow. Both problems have clear fixes, but the difference between a patch that lasts a week and one that lasts years is whether the drain gradient, the pipe and the underlying cause are all sorted together.

Why does aircon water leak inside instead of outside?

Your fan coil unit sits indoors and collects condensation in a shallow drip tray. That water is meant to flow, by gravity alone, down a small condensate pipe to a drain outside or in the service duct. There is no pump in most residential split units, so the pipe relies entirely on a downward slope the whole way.

When the water cannot leave, it overflows the tray and drips from the bottom of the indoor unit. The common triggers are all about that drainage path being interrupted or the coil producing more water than usual.

In a typical Singapore flat, the usual suspects are:

A drain pipe clogged with algae, biofilm and dust (the single most common cause)
A drain line with a sag, back-slope or a section that runs uphill
A cracked or dislodged drip tray, often after a poor servicing job
A frozen coil that melts all at once and floods past the tray
A loose or disconnected drain hose inside the wall or trunking

How does a blocked condensate drain cause dripping?

Condensate water is not clean. It carries dust, and in a warm damp pipe that dust feeds algae and slime, which slowly narrow the drain until it seals shut. Once blocked, the tray fills within minutes of the unit running, then spills over the front edge and drips into the room.

You can often confirm this yourself. If water only appears when the aircon runs and stops soon after you switch it off, and there is no ice, a blockage is the likely answer. A technician clears it by flushing the line and, on stubborn cases, using a vacuum pump or nitrogen to blow the clog out toward the outdoor end.

Why does my aircon form ice and then leak?

Ice on the copper coil or pipes means the coil is running colder than it should, so airborne moisture freezes onto it instead of dripping into the tray. When you switch off or the coil warms, all that ice melts at once and overwhelms the tray, so it leaks.

Two causes dominate. First, a dirty filter or fan restricts airflow, so the coil gets too cold. Second, low refrigerant (usually from a slow leak) drops the coil temperature and freezes it. A filter you can wash yourself; a refrigerant leak needs a technician to find, repair and recharge, because simply topping up gas on a leaking system is a short-lived fix.

Ice plus weak or warm airflow often means low refrigerant
Ice with a visibly dirty filter often means airflow starvation
Never chip ice off the coil; switch the unit off and let it thaw first

Blocked drain vs frozen coil: how to tell them apart

The fastest way to narrow it down is to look for ice and to notice when the dripping happens. These two clues separate most cases before anyone opens the unit.

Blocked drain: no ice, water drips while running, cooling still feels normal, worse in the first minutes
Frozen coil: visible frost or ice on coil or pipes, weak cold air, heavy dripping after you switch off as ice melts
Cracked tray or loose hose: dripping from one specific spot regardless of ice, sometimes only at certain angles
Both at once is possible: a frozen coil can also overload an already sluggish drain

What are the fixes that actually last?

A lasting repair treats the cause, not just the puddle. Clearing a blocked drain helps for a season, but if the pipe has a back-slope or the tray is cracked, the leak returns. Good technicians check the gradient of the drain line end to end, reseat or replace a damaged tray, and confirm the coil is not freezing before they call it done.

For recurring drips, the durable fixes usually involve some of the following:

Flush and vacuum the full condensate line, not just the visible end
Correct the drain gradient so the whole run slopes downward to the outlet
Replace a cracked drip tray or a perished, kinked drain hose
Trace and repair a refrigerant leak, then recharge to spec, rather than topping up
Set a regular servicing interval so biofilm never has time to fully block the line
Insulate exposed copper and drain pipes to cut condensation dripping outside the tray

When should you call a professional?

Washing the filter and wiping the tray are safe to do yourself. Beyond that, most fixes involve refrigerant, electrical connections, or opening up wall trunking, which are best left to a trained technician. Refrigerant handling in particular requires the right tools and care, and a wrong recharge can damage the compressor.

If the leak keeps coming back, if you see ice, or if the drip is near power points, wiring or a distribution board, get it looked at properly. Our team handles aircon drainage, coil and refrigerant work as part of general home electrical and cooling servicing, so the drain, the coil and any nearby wiring get checked together instead of patched one at a time. That is what turns a repeat leak into a fix that holds.

Frequently asked questions

Is a leaking aircon dangerous? The water itself is mostly a nuisance and can stain walls or ceilings, but water near power points, wiring or the indoor unit's electrical parts is a real hazard. Switch the unit off at the wall, keep the area dry, and get it inspected before running it again.

Can I fix a dripping aircon myself? You can safely wash the filter and wipe the drip tray, which resolves some airflow and minor cases. Clearing a fully blocked drain, correcting the pipe slope, replacing a tray, or handling refrigerant needs a technician with the right tools.

How often should I service my aircon in Singapore? For regular home use, a general clean every three to four months keeps the drain from clogging and the coil efficient. Heavier use or a home with more dust may need it more often; the point is to stop biofilm before it seals the drain.

Why does my aircon only leak on very hot or humid days? On hot, humid days the coil pulls far more moisture from the air, so the tray and drain carry a heavier load. A pipe that copes on a mild day can overflow on a humid one, which usually means the drain is partly blocked or the gradient is marginal and worth correcting.