Walk into a room and step into a wet patch. Look up. Water drops are sliding down the front of your aircon. The wall behind it has a damp shadow. Maybe there is already a small ring of mould forming.
This is one of the most common calls we get at Lion City Aircon. We run 6 teams across Singapore doing 30+ jobs a day, and water leakage shows up multiple times daily, especially in older HDB flats and condos that haven’t had servicing in 6 months or more.
Water leaks are almost always fixable, usually in a single visit. The not so good news is that if you ignore them, the damage compounds. Peeling paint, swollen skirting, mould on ceilings, and in the worst cases, electrical risk from water reaching the indoor unit’s PCB.
This guide covers every reason your aircon is leaking water in Singapore, how to tell which cause you’re dealing with, what we actually do to fix it, and how to stop it from coming back. It’s based on what we see in real Singapore homes, not generic American HVAC content recycled for SG.
The Real Reason Aircons Drip Water (And Why It’s Almost Always About the Drain Pipe)
Before we get to causes, you need to know one thing: your aircon is supposed to produce water. That’s how it cools.
When warm Singapore air hits the cold evaporator coil inside your indoor unit, the moisture in the air condenses. Exactly like droplets forming on a cold glass of iced water. A typical HDB sized unit produces between 1 and 3 litres of condensation per day during heavy use. That water collects in a drip tray under the coil, then flows out through a small drain pipe that exits through your wall (usually to your service balcony, ledge, or PVC riser).
So when water starts dripping inside your home instead of outside, the question is never “why is there water?” The question is: “why isn’t the water getting out?”
And 7 times out of 10, the answer is the drain pipe. That’s why the very first thing our technicians check on any leak call is the drainage line. Not the gas, not the coil, not the filter. The drain pipe.
The 6 Causes of Aircon Water Leaks in Singapore (Ranked by How Often We See Them)
1. Clogged Drain Pipe (by far the #1 cause)
Singapore’s humidity means your drain pipe is permanently damp. Dust gets sucked into the indoor unit, sticks to the wet inside of the pipe, and over time forms a soft sludge. Add a bit of algae (which thrives in dark, wet plastic tubes) and bacteria, and within 6 to 12 months you’ve got a blockage thick enough to back the water up.
When the pipe blocks, water has nowhere to go. It fills the drip tray, overflows, and drips down the front of your indoor unit. Usually from the bottom corners, sometimes from the middle.
How to spot it: Water dripping steadily from the indoor unit while the aircon is running. Often worse on humid days when the unit produces more condensation. May start as occasional drops and worsen over a few weeks.
How we fix it: A proper drain pipe flush using a vacuum pump on the outdoor end of the pipe. Not blowing into it from inside (which just packs the sludge tighter). For severe blockages, we use a chemical flush followed by pressurised water. A clean drain pipe flush is part of every quarterly aircon servicing we do. If your last service skipped this step or rushed it, you’re on the road to a leak.
2. Dirty Air Filter Causing the Coil to Freeze
When your air filter is clogged with dust, air can’t move across the evaporator coil at the proper rate. With reduced airflow, the coil drops below 0°C and starts forming a layer of ice on the fins.
You won’t notice the ice. It’s hidden inside the unit. What you will notice is the cooling getting weaker. Then, when you switch the aircon off, the ice melts all at once. That sudden flood of meltwater overwhelms the drip tray and spills out as a heavy drip.
How to spot it: Aircon was leaking after you turned it off, not while running. Or weak cooling for the past few days, then a leak. Filters look grey or visibly furry when you pull them out.
How we fix it: Clean filters (you can do this yourself monthly). But if the coil has frozen repeatedly, the fins may have bent and the coil itself needs proper cleaning. This is when a basic servicing turns into a chemical wash situation.
3. Low Refrigerant Gas (Coil Freezing From the Other Direction)
If your aircon is undercharged on refrigerant (usually because of a slow leak in the copper piping), the coil pressure drops, the coil gets too cold, and ice forms. Same outcome as a dirty filter (meltwater leak), but a different root cause.
Low gas usually means there’s a leak somewhere in the system. Just topping up gas without finding the leak is a waste of money. The gas will be gone in weeks.
How to spot it: Weak cooling for weeks or months getting progressively worse. Ice or frost visible on the copper pipes connecting indoor to outdoor unit. Aircon running 24/7 but never quite cooling. More on aircon gas top-ups here.
How we fix it: Pressure test the system with nitrogen to find the leak, repair or replace the leaking section, vacuum the system, recharge with the correct gas type (R32, R410A, or R22 depending on your unit).
4. Damaged, Cracked, or Misaligned Drip Tray
The drip tray (also called the drain pan) sits under your evaporator coil and catches the condensation before it flows out. After 8 to 10 years, the plastic can crack from heat cycling, or rust through if it’s an older metal tray. Sometimes during a previous servicing or repair, the tray gets reinstalled crooked. Even a 5mm tilt is enough to spill water over the edge.
How to spot it: Leak is from a specific corner or section of the indoor unit, not evenly across. The drain pipe checks out clean but water still drips. Common in units over 8 years old.
How we fix it: Inspect, realign, or replace. Drip tray replacements vary by aircon brand. Daikin, Mitsubishi, Panasonic, and Hitachi all have different part numbers. We source genuine parts where we can.
5. Poor Original Installation
The drain pipe must be installed with a slight downward slope all the way from the indoor unit to the exit point. Usually 1cm of drop per 1m of horizontal run. If the original installer ran it flat, or worse, sloping upward over a beam or pipe, water never drains properly from day one.
This often shows up as a leak within the first year of a brand new installation, or after a renovation where someone moved pipes around.
How to spot it: Brand new aircon leaking. Recent renovation completed near the aircon. Drain pipe visibly running flat or uphill at any point.
How we fix it: Re-route the drain pipe with proper gradient. In some cases the original installer used pipe diameter too small for the unit’s water output and we need to upsize.
6. Wall Condensation (Not Actually a Leak)
Sometimes what looks like an aircon leak is actually condensation forming on the wall or ceiling around the unit. Caused by warm humid air meeting cold pipe insulation that has dried out or come loose. The water isn’t coming from inside the aircon at all.
How to spot it: Wet patches on the wall around the indoor unit, not dripping from the unit itself. Often worst in rooms with poor ventilation or the aircon running 8+ hours daily.
How we fix it: Replace the foam insulation on the refrigerant pipes (the white or grey foam sleeve). This is the kind of issue covered in our guide to aircon condensation on walls and ceilings.
What to Do Right Now if Your Aircon Is Leaking
Whether you call us today or tomorrow, do these things first:
- Switch the aircon off at the wall. Running it while it’s leaking risks water reaching the PCB.
- Put a bucket or towel under the unit. The drip tray will continue to empty for a while even after you switch off.
- Don’t try to unclog the drain pipe yourself by blowing into it. This is the most common DIY mistake we see. Blowing into the indoor end packs the sludge tighter against the outdoor exit and turns a 30 minute fix into a 90 minute one.
- Take a photo of the leak point. Send it to us on WhatsApp at +65 8818 5781. We can usually tell you the likely cause before we send a team out, and price the visit accurately.
How Much Does Fixing a Water Leak Cost in Singapore?
Lion City Aircon’s pricing is the same across Singapore. HDB, condo, landed, same rate. For water leak diagnosis and repair:
- Drain pipe vacuum and flush: covered in standard servicing ($35 to $50 per unit)
- Chemical flush for severe blockage: from $90 per unit
- Drip tray replacement: from $120 (parts + labour)
- Gas top-up (if low refrigerant): from $130 per system
- Pipe re-routing for installation issues: quoted on site after inspection
If you have an active annual maintenance contract with us, water leak repairs from drain pipe blockages are included free between scheduled visits. That’s one of the perks contract customers get that one off jobs don’t.
How to Prevent Water Leaks From Happening Again
Once you’ve had one water leak, the cause matters. If it was a clogged drain pipe (which it usually is), the same blockage will return in 6 to 12 months unless servicing is done properly each visit.
This is the part most homeowners don’t realise: quarterly aircon servicing exists primarily because of the drain pipe, not because of cooling. Cooling efficiency drops slowly over many months. But a drain pipe can go from “fine” to “flooding your floor” in a matter of weeks once enough sludge accumulates.
Our quarterly servicing always includes:
- Drain pipe vacuum flush (outdoor end) to clear the full length
- Drip tray cleaning and alignment check
- Coil inspection for ice formation patterns
- Pipe insulation check for damage
- Gas pressure check (basic, not a full top-up unless needed)
The right service frequency depends on usage. See our guide on how often to service your aircon in Singapore.
Frequently Asked Questions About Aircon Water Leaks
Can I use a leaking aircon until I get it fixed?
Short term, yes. If you turn it off immediately when water appears and place a towel underneath. Long term, no. The water often reaches the indoor unit’s electrical components and can short the PCB, turning a $50 fix into a $400+ board replacement.
Why does my aircon only leak sometimes, not every time?
This is common with partial drain pipe blockages. When the aircon runs in shorter cycles or in dry mode, less condensation forms and the partially blocked pipe can still handle it. When you run it for hours on humid days, water volume increases past what the blocked pipe can pass and overflows. It will get worse over time. Don’t ignore it.
The water is dripping from the outdoor unit. Is that the same problem?
No. Water dripping from the outdoor unit is normal in most cases. The outdoor unit’s water comes from the drain pipe doing its job (draining condensation out of the building). What’s not normal is a sudden large volume of water from the outdoor unit, which can indicate a refrigerant or condenser issue.
Will a chemical wash stop the leak?
A chemical wash deep cleans the indoor coil and drain pan but only flushes the drain pipe as part of the process. If your leak is from a clogged drain pipe, a chemical wash will fix it. If it’s from a cracked tray or installation problem, a chemical wash won’t help. You need a targeted repair. We diagnose first before recommending the service. More on aircon chemical wash here.
My aircon is brand new and already leaking. Is that the installer’s fault?
Usually yes. New unit leaks are almost always installation issues. Flat or uphill drain pipe routing, undersized pipe diameter, missing pipe insulation, or a misaligned indoor unit. Contact your installer first if you’re still within their workmanship warranty (typically 1 year). If they can’t or won’t fix it, we can take over.
How long does fixing a water leak take?
Most drain pipe blockages take 30 to 60 minutes per unit to fully clear. Drip tray replacements take 60 to 90 minutes. Pipe re-routing for installation issues can take 2 to 4 hours depending on complexity. We carry the tools and common parts on the truck to fix most leaks in a single visit. No second appointment needed.
Can I just clean the drain pipe myself?
You can clean filters and the surface of the indoor unit, but the drain pipe needs a vacuum pump applied to the outdoor end. Without that, you’ll push sludge deeper. DIY cleaning helps maintenance between professional visits but isn’t a substitute for it. See our guide on DIY versus professional aircon cleaning.
What if my unit keeps leaking even after servicing?
That means the servicing didn’t clear the full drain pipe properly, or the cause is something other than drainage. Usually a damaged tray or a refrigerant issue. A reliable aircon company will come back for free to diagnose. We do. Every job we complete comes with a workmanship guarantee.
Stop the Leak Today
If your aircon is dripping water right now, the longer you wait, the more damage gets done. To your walls, your floors, and eventually the unit itself.
WhatsApp us at +65 8818 5781 with a photo of the leak. We’ll diagnose remotely where we can and get a team to your home. Same day in most cases. We service all of Singapore at the same price. HDB, condo, landed, doesn’t matter. 22,000+ jobs done since 2016, 5.0★ across 1,500+ Google reviews, BizSafe Level 3 certified.
No scare tactics. No upselling. If your leak is a 30 minute drain flush, we’ll tell you that and price it accordingly. If it’s something more serious, we’ll show you what we found before doing anything.
WhatsApp Lion City Aircon · Call +65 8818 5781 · Book online
Related reading: Aircon jelly explained · Chemical wash vs general servicing
