Aircon Troubleshooting · Singapore · Updated July 2026
Why Is My Aircon Leaking or Dripping Water?
Water dripping from the front of the indoor unit is almost always a drainage problem (a blocked pipe or algae) or a frozen coil melting — here’s how to tell which and how we fix it.
The short answer
Water dripping from the indoor unit almost always means it can’t drain properly — a blocked or clogged drainage pipe or algae in the drain tray is the most common cause. The next most common is a frozen cooling coil melting, caused by low gas or a dirty filter/coil. Less often it’s a cracked drain pan or a badly sloped drain pipe. Turn the unit off to avoid water damage and book a technician.
Where the water actually comes from
Singapore’s air is very humid — it holds a lot of moisture. Inside your indoor unit (the fan coil unit) sits a cold evaporator coil — the “fan coil” that the blower pushes room air across to cool it. When warm, humid air meets that cold coil, the moisture in it condenses into water droplets — exactly the way a cold drink sweats on a hot day.
That condensation runs down the coil and collects in a drip tray (the condensate tray) directly beneath it. From the tray, a drain pipe carries the water away — usually out through the wall to the outside, or to a bathroom floor trap. When the path is clear, this happens quietly in the background and you never see a drop indoors.
The leak begins when that drainage path gets clogged — most often in the drip tray itself or somewhere along the pipe. With nowhere to go, water fills the tray faster than it can drain, rises to the edge, and overflows out of the front of the indoor unit into your room.
Why the drain gets blocked
- • Algae and slime. Warm, damp, still water in the tray and pipe is ideal for algae — it grows into a slimy plug that seals the outlet. The most common cause in Singapore’s climate.
- • Dust and dirt. Grime washed off a dirty filter and coil settles in the tray and hardens into sludge that chokes the drain.
- • Mould build-up. A neglected coil and tray grow mould that sheds into the drain and blocks it.
- • Blocked or submerged pipe outlet. The outdoor end can be kinked, clogged with leaves and debris, or sitting in standing water that stops it draining.
- • Badly sloped pipe. If the drain pipe runs too flat — or slopes back toward the unit — gravity can’t pull the water out, so it pools and backs up.
The detailed causes and the fix for each are below.
Is it normal for an aircon to drip water?
It depends entirely on where the water comes from. One kind of dripping is completely normal — the other means something is blocked.
Normal — water outside
Water dripping from the drain pipe outside your window, or from the outdoor unit, is normal. Your aircon removes moisture from the air and drains it outside — expect more of it on humid or rainy days. As long as it stays outside, there’s nothing to fix.
Not normal — water indoors
Water dripping from the indoor unit inside your home — from the front of the unit, or where the pipe enters the wall — is not normal. The condensation can’t drain away and is overflowing, and it needs attention before it reaches your wiring, ceiling, or walls.
A separate case is a leaking drain pipe — water dripping along the pipe itself rather than from the unit. That’s usually a slipped joint or a sweating, uninsulated pipe, and it needs re-sealing or re-insulating rather than just a flush.
Quick diagnosis by symptom
Match what you’re seeing to the likely cause and typical fix.
| What you notice | Likely cause | Typical fix |
|---|---|---|
| Steady drip from the front of the indoor unit | Blocked drain pipe | Drainage flush |
| Water + slimy residue in tray | Algae in drain tray | Chemical wash |
| Drips after running a while; ice on pipes | Frozen coil / low gas | Gas top-up + wash |
| Water inside even when filter is clean | Cracked pan / badly sloped pipe | Repair (diagnosis first) |
| Leak worsens on humid/rainy days | Overflowing water from dirty coil | Chemical wash |
| Dripping along the pipe, not from the unit | Slipped joint / worn pipe insulation | Repair (re-seal / re-insulate) |
| Water only outside, from the drain pipe | Normal condensation draining | No fix needed |
Common causes — and the fix for each
From most to least common in Singapore homes.
Blocked or clogged drainage pipe (most common)
Algae and dust build a slimy clog inside the pipe, so condensation backs up and overflows the tray instead of draining outside. The single most common cause of a leaking indoor unit.
Drainage flushAlgae or mould in the drain tray
Stagnant water in the tray grows slime that blocks the outlet. Very common in Singapore’s humidity if the unit hasn’t been deep-cleaned in a while.
Chemical washFrozen cooling coil melting
Low gas or restricted airflow ices over the coil. When the ice melts, the run-off overflows the tray faster than it can drain — so you see water dripping after the unit has run a while.
Gas top-upDirty air filter
A clogged filter chokes airflow, which freezes the coil; when it later thaws, the melt-water drips out. A leading and easily-missed cause of a leaking unit.
General servicingCracked or disconnected drain pan/pipe
Physical damage to the pan, or a joint that has slipped apart, lets water escape inside the unit instead of being carried outside. Needs a repair, not a clean.
Aircon repairPoorly installed or badly sloped drain pipe
If the drain pipe was laid too flat — or even sloping back toward the unit — water never fully drains and eventually overflows. Common after a rushed or DIY installation.
Aircon repairOverflowing water from a dirty coil
A mould-caked cooling coil sheds more water than the tray can handle, so it overflows — especially on humid or rainy days when the unit pulls the most moisture from the air.
Chemical washLoose pipe joint or failed insulation
A disconnected joint, or a sweating uninsulated pipe, drips water along its length rather than at the unit. Re-sealing the joint or re-insulating the pipe stops it.
Aircon repairDrain pump failure
Units mounted below their drain outlet rely on a small pump to push water out. When that pump clogs or fails, the water has nowhere to go and overflows the tray — common in ceiling-cassette and some high-wall units.
Aircon repairWhat you can check yourself first
These are free and safe to try before booking a visit.
- 1Turn the aircon off at the remote and the breaker to stop water reaching the wiring and the ceiling.
- 2Place a towel or container under the drip to protect the floor and furniture.
- 3Remove and rinse the washable filter — a clogged filter is a leading cause of coil freezing.
- 4Check the outdoor end of the drain pipe isn’t submerged, kinked, or blocked by debris.
- 5Look for ice on the copper pipes; if present, switch off and let it thaw before booking.
How to fix a leaking aircon
Some fixes are a quick patch; one actually solves the cause. Here’s what each does — and where DIY stops working.
Empty the drip tray
Quick reliefIf water is overflowing right now, switch the unit off and empty the drip tray to stop the drip and protect your floor. It’s only a stop-gap, though — the tray fills up again until the drainage itself is cleared.
Clear the blockage you can reach
DIY fixClean out the drip tray, and check the outdoor end of the drain pipe isn’t kinked, submerged, or blocked by leaves. If the clog is right at the tray or the outlet, clearing it can get the water draining again.
If the blockage is inside the pipe, it comes back
Needs a proHere’s the catch: when the algae or sludge plug sits deep inside the drain pipe — where you can’t reach it — emptying the tray and cleaning the outlet won’t hold. The water backs up and the leak returns within days. The pipe has to be flushed clear with a pump or wet-vac, and the algae that caused it removed at the source.
The lasting fix: clear the drain at the source
If the leak keeps coming back, the clog is inside the pipe or the tray and coil are caked with algae. We flush the drain line clear and remove the build-up with a general cleaning or, for a heavier clog, a chemical wash — so it drains normally again, not just until next week. Same-day, island-wide, with the price confirmed before we start. Not sure which level you need? Compare the aircon cleaning options.
How to stop your aircon leaking again
Almost every leak traces back to a drain that was never kept clear. A little upkeep prevents most of them.
- Service the unit every 3–4 months — regular cleaning clears the algae and dust that clog the drain in the first place.
- Ask for a drain-line flush during servicing so the pipe stays clear before it ever backs up.
- Rinse or replace the filter monthly — a clean filter keeps airflow up and stops the coil from freezing.
- Keep the outdoor drain outlet clear of leaves, debris, and standing water.
- Have the drain pipe’s slope checked if the unit was recently installed or relocated.
The simplest safeguard is routine aircon servicing — it keeps the drain, tray, and coil clear so condensation always has somewhere to go.
When to call a technician
Water and electrics don’t mix — a leaking indoor unit sits right next to live wiring and the control board, so keep it switched off until it’s fixed. Most leaks come down to a clog or algae you can’t reach safely, or a cracked pan and slipped joint that need re-sealing; the longer water keeps escaping, the more it risks your ceiling, walls, and furniture.
We find the exact cause on-site, tell you the price before any work begins, and can usually fix it the same day — our aircon repair service covers leaks island-wide across Singapore.
Other aircon problems
Aircon leaking water — FAQs
Why is my aircon dripping water inside the house?
Is it normal for my aircon to drip water outside?
My aircon drain pipe is leaking — what causes that?
Is it safe to use my aircon while it’s leaking?
Why does my aircon only leak on humid or rainy days?
Can I clear the drain pipe myself?
How much does it cost to fix an aircon water leak?
Will a chemical wash stop the leaking?
My aircon leaks but still cools — is it serious?
Why is my aircon leaking water after servicing?
Still leaking? We’ll sort it today.
Same-day diagnosis across Singapore. We confirm the price with you before any work begins.