10 Common Reasons for Aircon Leaking Water and How to Tackle

In Singapore’s hot and humid climate, a reliable air conditioner is essential for comfort and health. Yet one of the most common issues homeowners face is aircon leaking water. A problem that can damage ceilings, flooring, and even electrical fixtures if left unresolved. 

According to the National Environment Agency (NEA), proper aircon maintenance and ventilation are key to preventing moisture accumulation and related issues. Faulty drainage, clogged filters, and poor installation are common culprits behind what causes aircon to leak. 

In this guide, SuperClean SG explains how to spot aircon leaks, understand their causes, and fix them with expert advice—so your cooling stays efficient and your home stays fresh.

Understanding Why Your Aircon is Leaking & Its Consequences

Aircon leaking water is one of the most common issues faced by homeowners in Singapore’s humid climate. While some condensation is normal, visible dripping or pooling signals a problem that needs to be addresses—so it doesn’t lead to water damage, mold, and reduced cooling efficiency. 

To understand what causes aircon to leak, it helps to know how your unit handles moisture. When warm, humid air passes over the cold evaporator coils, condensation forms, and collects in a drain pan before flowing out through a condensate line.

If the drainage path becomes blocked or damaged—or if the coils freeze due to issues like aircon not blowing cool air—water can overflow and leak indoors. Left unresolved, this can cause several serious issues, including: 

• Structural damage: Continuous water exposure can weaken walls, ceilings, and flooring, leading to costly repairs.
• Mold and mildew growth: Persistent dampness encourages mold, which spreads quickly through your HVAC system.
• Health risks: Mold spores may trigger allergies, asthma, or other respiratory issues.
• Electrical hazards: Water entering electrical components increases the risk of short circuits or fires.
• Higher energy bills: A malfunctioning aircon works harder to cool, using more electricity.
• Premature system failure: Ongoing water damage can cause the entire unit to fail before its expected lifespan. 

Recognizing these consequences helps prevent extensive damage and keeps your aircon running safely and efficiently.

Signs of  Aircon is Leaking Water

Now, the thing is how to tell if your aircon leaking water is a minor issue or something more serious? Here are the key signs to watch out for that may indicate aircon to leak: 

• Visible water dripping or pooling: The clearest sign is water dripping from your indoor unit or pooling on the floor beneath it. 
• Water stains on walls or ceilings: Yellow or brown stains near the unit or on the ceiling suggest ongoing aircon water leakage. 

• Musty odors: A damp, moldy smell near the aircon often points to trapped moisture or poor drainage. 

• Reduced cooling performance: If your aircon is not cooling effectively or struggles to keep the room comfortable, drainage or condensation issues may be to blame. 

• Unusual sounds: Gurgling or dripping noises often mean water is stuck where it shouldn’t be inside the system. 
• High Humidity Levels: When your aircon is not blowing cool air properly, humidity may stay high, signaling a drainage or efficiency problem.

10 Common Causes of Aircon Water Leakage & Solutions

Before you can fix an aircon leaking water, it’s important to understand what causes aircon to leak. Water leaks may look minor, but if left untreated, they can damage walls, ceilings, and even your cooling system. 

Here are 10 of the most common causes and practical solutions every homeowner in Singapore should know.

1. Clogged Drain Line

A clogged condensate drain line is the most common cause of aircon water leakage. Over time, dirt, algae, and dust block the pipe, preventing proper drainage. When water backs up, it overflows from the pan, causing dripping or damp walls.

Solution: 

• Turn off your aircon before attempting any cleaning.
• Use a wet/dry vacuum to suction out debris from the drain line.
• Flush the line with white vinegar or a mild bleach solution (1:10 ratio).
• Pour a cup of vinegar every 2–3 months for prevention.

2. Full of Overflowing Drain Pan

During periods of high humidity, your drain pan collects more condensation than usual. When the pan becomes full and cannot drain fast enough, water begins to overflow, often dripping from the bottom of your aircon unit. This is common in units with old or undersized pans.

Solution: 

• Check if the drain pan is full or stagnant with water.
• Clean out the pan and ensure the drain line is unobstructed.
• If overflow continues, inspect for pump or possible drainage issues.

3. Damaged of Rusted Drain Pan

Over time, constant exposure to water can corrode or crack your aircon’s drain pan, especially in older systems (10+ years). Once this happens, condensation leaks before it can reach the drain line, creating puddles beneath the indoor unit.

Solution: 

• Seal small cracks temporarily with waterproof epoxy or sealant.
• Replace severely rusted or damaged pans for a long-term solution.
• Have aircon repair experts perform replacements to prevent unit damage.

4. Dirty Air Filters

When air filters are clogged with dust, pet hair, or debris, airflow becomes restricted. This causes the evaporator coil to get too cold and eventually freeze. As the ice melts, excess water overwhelms the drainage system, leading to aircon leaking water and aircon not cooling efficiently.

Solution: 

• Turn off the unit and let the ice melt fully.
• Clean or replace filters every 1–3 months.
• Keep vents and indoor areas free from obstructions.

5. Frozen Evaporator Coils

Your evaporator coils play a vital role in absorbing heat and humidity. When they freeze due to airflow problems, low refrigerant, or mechanical faults, ice forms on the coils. Once thawed, this ice melts into a large volume of water that your drain pan cannot handle, leading to aircon leaking water. 

Solution: 

• Turn off the aircon and allow coils to thaw completely.
• Check and clean filters and vents for airflow issues.
• If freezing persists, inspect refrigerant pressure and mechanical parts.

This isn’t a DIY fix. Refrigerant handling requires certified expertise. Consider hiring professional experts like SuperClean SG, whose trained aircon technicians can safely diagnose and repair refrigerant or mechanical issues for long-term reliability.

6. Low Refrigerant Levels

A low refrigerant level reduces internal pressure, making the evaporator coil too cold and prone to freezing. When the ice melts, you’ll notice excess water leaking. You may also experience aircon not blowing cool air, hissing noises, or reduced cooling power.

Solution: 

• Turn off the unit if you suspect low refrigerant (signs: aircon not cooling or bubbling noise).
• Have a licensed technician:
  • Detects and seals refrigerant leaks.
  • Recharge the system to the proper level.
  • Inspect for compressor or valve issues.

7. Improper Installation

If your aircon was installed unevenly or incorrectly, it can cause improper water drainage. An indoor unit that tilts the wrong way traps water in the drain pan, forcing it to overflow into your room instead of draining out properly.

Solution: 

• Check the alignment using a spirit level.
• Ensure your wall-mounted aircon tilts slightly (3–5°) toward the drain line.
• For window units, tilt outward to encourage drainage.
• Contact aircon installation specialists to re-level or re-install your unit correctly.

8. Faulty Condensate Pump

In installations where gravity drainage isn’t possible (such as ceiling or basement units), a condensate pump is used to remove water. When the pump fails, water collects and eventually spills from the drain pan.

Solution: 

• Check that the pump is powered and not clogged.
• Pour water into the pump’s reservoir to test activation.
• Clean or replace if non-functional.

9. Leaking Condenser Coil

Outdoor condenser coils often collect dirt and moisture, leading to corrosion or small cracks that cause slow leaks. Over time, this reduces cooling efficiency and can worsen aircon leaking water problems if not fixed promptly.

Solution: 

• Schedule routine aircon maintenance services for coil cleaning.
• Keep the outdoor unit free from leaves and dust.
• Replace damaged coils to maintain system efficiency.

10. Air Leakage Around Vents or Ducts

Outdoor condenser coils are constantly exposed to Singapore’s humid air and environmental debris. Over time, dirt, leaves, and moisture can cause corrosion, small cracks, or blockages, leading to slow leaks and reduced cooling efficiency.

Solution: 

• Turn off your aircon and gently clean the outdoor condenser fins with a soft brush or low-pressure water.
• Keep the outdoor unit area clear of leaves, debris, and plants to maintain airflow.
• Inspect for visible corrosion or damage—use coil cleaner sprays available at hardware stores.

DIY Aircon Leaking Water Fixes

Before calling for a technician, some issues actually can be safely managed at home. Understanding what causes the aircon to leak helps you take quick action to prevent further damage or costly repairs. 

Here are a few practical troubleshooting steps you can try:

1. Turn off your aircon system: Prevents further water damage and lets frozen parts thaw safely.
2. Check and replace air filters: Dirty filters are a common cause of cooling and leakage problems.
3. Inspect the drain pan: Look for cracks, rust, or overflow, and clean away dirt or algae.
4. Clear visible blockages: Remove any debris around the drain line opening.
5. Ensure the unit is level: Use a spirit level and make small adjustments if needed.
6. Check the outdoor condensate pipe: Clear away dirt, leaves, or insect nests that may clog it.
7. Flush the drain line: Pour white vinegar followed by warm water to dissolve light buildup.

If these steps don’t resolve the issue, or if you’re uncomfortable performing any of these tasks, it’s time to contact a professional for expert assistance.

Aircon Maintenance Tips to Avoid Water Leakage

Preventing aircon water leakage is easier and less costly than dealing with the aftermath. Here are proven aircon maintenance tips from our SuperClean SG’s technicians:

1. Schedule regular professional servicing: We recommend professional aircon servicing every 3-4 months in Singapore’s climate, where humidity and usage are high.
2. Change or clean air filters regularly: Mark calendar reminders to check filters monthly and replace or clean them every 1-2 months during heavy usage periods.
3. Keep indoor and outdoor units clean: Ensure the area around your outdoor condenser unit remains free of debris, leaves, and vegetation that might block airflow or drainage. 
4. Monitor drain line outlets: Periodically check that water is flowing properly from the condensate drain line when your system is operating.
5. Use algae tablets or vinegar treatments: These can help prevent biological growth and buildup in drain lines. Choose products that are safe for your aircon system and apply them regularly as part of routine maintenance.
6. Maintain optimal humidity levels: In extremely humid environments, using a dehumidifier can reduce the strain on your aircon system.
7. Consider upgrading older units: Systems older than 10-15 years are more prone to leakage problems and are less energy-efficient. Upgrading can prevent issues while reducing electricity costs.

When to Call Professional Aircon Servicing

While some minor cases of aircon leaking water can be solved with simple maintenance, certain situations require professional expertise to ensure safety and efficiency. Here are common scenarios when you should call for professional aircon servicing:

Regular aircon maintenance prevents water leakage, boosts cooling efficiency, extends system lifespan, and keeps indoor air clean. Calling a professional servicing ensures all parts—from coils to drain lines—are safely inspected and cleaned.

FAQs About Aircon Leaking Water

1. Is it normal for my aircon to be leaking water? 

A small amount of condensation near your aircon is normal, especially in humid climates like Singapore. However, constant dripping, pooling water, or visible stains indicate a drainage or maintenance issue that needs attention. If you notice persistent leaks, turn off the unit and inspect for blockages or frozen coils.

2. Can I still use my aircon while it’s leaking? 

It’s not recommended to continue using an aircon that’s leaking water. Operating it may worsen the issue or cause electrical damage. Switch it off immediately, clean any visible water, and check if the drain pan or filters are clogged before restarting.

3. How often should I service my aircon to prevent leaks? 

In Singapore’s humid environment, professional aircon servicing is recommended every 1-3 months. Regular maintenance keeps filters clean, drain lines clear, and components working efficiently. It helps prevent most water leakage issues before they start. 

4. Does aircon leaking water mean I need a new unit? 

Not always. Most aircon water leaks are caused by clogs, dirt buildup, or minor component wear. However, if your system is over 10 years old and frequently leaks despite servicing, it may be more cost-effective to replace it with a newer model.

Conclusion: Taking Action on Aircon Water Leakage

Aircon leaking water is a common problem that can stem from clogged drain lines, dirty filters, or mechanical faults. Recognising early signs and understanding what causes aircon to leak helps you act fast—whether through simple DIY fixes or by calling a professional. 

Regular aircon maintenance keeps your unit running efficiently and your indoor air fresh. Clean filters, clear drainage, and timely servicing reduce the risk of leaks and improve cooling performance. By staying proactive, you protect your home, save on energy costs, and enjoy lasting comfort in Singapore’s humid climate.