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Water Leaking from Air Conditioner Inside


Imagine you’ve come inside after a hot, busy day.  You flick on the air conditioner and head to the kitchen to start dinner.  Between the microwave running, pans sizzling, and tap running, you don’t hear much else.  But once you stop cooking and start dishing up, you hear dripping.

You stop and listen.  You look at the tap – no water dripping there.  You walk to the bathroom to check – no water dripping in the basin or shower.  What is that noise?!

Then you walk into the cool living area.  There it is: water dripping from the AC.  So much water in fact that there’s a puddle underneath the AC indoor unit!  Great, another mess to clean up.

Water dripping from AC indoor unit is not just annoying, it’s also a sign that there is an underlying issue with your air conditioner.  There are many reasons why water may be coming out where it shouldn’t.  The issues and solutions range from simple, routine fixes to major faults to be addressed.

We’ll explore common questions and solutions for those dealing with an air conditioner leaking water inside.  While a nice cold drink or swim is appreciated on a hot day, water from your air conditioner is not something you want!

This week’s question:  

Why is my air conditioner leaking water inside the apartment?

There are a wide range of causes when it comes to air conditioner water leaks.  Each specific source requires a slightly different treatment to resolve it:

Blocked Drain

One of the most common causes of water from AC indoor unit is a blocked drain.  The drainpipe in an air conditioner carries away condensation from the indoor drain pan, which develops normally during the reverse cycle air conditioning cycle.

Any dirt, debris, mould, algae, etc. that finds its way into the drain pan also needs to make it out through the drainpipe.  If the mass is too large or if the drainage pipe breaks in any way, water can back up and start leaking inside the apartment, home, or business.

Regular cleaning of condensate drains is essential to help prevent water build up and leakage in all the wrong places.  Some of this can be completed at home, however routine maintenance by a professional is typically recommended.

Dirty Air Filters

Dirty air filters are one of the most common causes of water dripping from an AC indoor unit.  Blocked or restricted return air filters reduce airflow back to the air conditioner, specifically the indoor evaporator coil.

When a dirty filter affects airflow, the coil can get too cold and start icing up.  When the ice begins to melt (either when the aircon is turned off and/or filters cleaned), the ice begins to melt and leak out of the indoor unit.

It is recommended to check filters monthly or at least at the start of each season, and clean filters when dirty.  When the media wears too thin, replacement of the filter/s is the next step.


Dirty return air filters blocking airflow ac indoor unit



Low Airflow

Like with dirty air filters, anything that results in low airflow can end up with water leaking.  This includes blocked or dirty evaporator coil, incorrect settings, obstructions around the indoor unit, faulty fan motor, and other faulty AC component/s that result in reduced airflow across the indoor coil.

An air conditioning repair service can address all issues, with repair of faulty components and completion of routine maintenance tasks.  Some low airflow issues can be prevented (e.g. obstructions), while others are not so preventable (e.g. faulty fan motor due to motor fusion or storm surge).

Poor AC Installation

Incorrect installation of an air conditioner head unit, drip tray, and/or drainpipe can result to water leaks.  Common issues include AC not installed in correct position, the drain pan being undersized (or not installed at all!), and incorrect fall on the drain.

While it’s difficult to directly control the workmanship of an HVAC installer, you do have the power to select a reputable air conditioner installer.  It’s recommended to consult a fully qualified HVAC Mechanic for a new air conditioner installation, rather than an Electricians with a restricted HVAC licence.  There are significant differences between the trades.

Damaged Drain or Drip Tray

Like most things, drains and drain trays can wear out over time.  They may crack, rust, or become damaged in some other way.

When this happens, water can not track from the drain pan, down the drainpipe, and away from the aircon indoor unit as design.  As a result, water can find a new route and leak out in all sorts of undesirable locations.

Regular inspection of the drain components is key to detecting possible damage.  Repair or replacement actions can then be undertaken.

Damaged AC indoor unit

Unlike the drain, and air conditioner indoor unit is not so easy to fix if it is damaged.  Sometimes head units can develop a hairline fracture within the chassis.  In this case, water leaks out in a random location from the indoor unit.

Unfortunately, repairs are not usually possible or financially viable if a hairline crack occurs within the indoor unit.  In this case, replacement of the whole system is typically recommended.

Refrigerant Leaks

Another common cause of water dripping from an air conditioner is a refrigerant leak.  Like low air flow, low refrigerant pressure impacts the ability of the indoor unit to operate correctly.  This can result in ice build up that later melts.

Testing and assessing gas pressures is best left to an HVAC expert.  They can also help assess whether gas repairs or system replacement would be the best course of action.

If the system is under warranty, it would be recommended to contact the installer to discuss options.  They may refer you to the manufacturer if this will be the most efficient option for you in terms of time, money, and resolution.

Faulty Condensate Pump

If there is a condensate pump installed, this can certainly be a source of water leaking inside an apartment, house, or business.  Water leaks can stem from a faulty or blocked condensate pump or pump drainage line.

Drain pump components may just need a service to resolve the leaking, which involves disassembling the pump and thoroughly cleaning it out.  Pump servicing is recommended more frequently than AC unit servicing.  However, if the pump is failed or inefficient, replacement of the pump may be required.


Old condensate pump under wall split systemNew mini blanc pump installed under wall split system


Addressing these AC water leak issues proactively through regular maintenance and inspection is recommended.  Basic DIY AC service checks includes filter cleaning and drain inspections.

Professional air conditioning service checks will include refrigerant pressure checks and AC component testing.  Either way, prevention is key to preventing complicated repairs and further damage to your air conditioner, property, and even yourself and those around you.

How to fix air conditioner leaking water inside?

Here are 7 steps to help resolve the issue of your air conditioner leaking water inside the apartment, house, or business:

Monitoring Temperature Settings

Avoid setting the temperature too low at all times, especially in humid conditions which are standard for Summer in Brisbane.  Temperature set too low, especially when humid, can result in excessive condensation and water leakage.

Clearing the Drain Line.

Use a wet/dry vacuum to suck out any debris or blockage via the outdoor drain outlet.  For stubborn blockages, a plumbing snake or a commercial cleaning solution may be required.

Servicing Air Filters.

Check return air filters every 1-3 months, and clean when dirty.  For washable filters, use mild detergent and water and ensure they are completely dry before reinserting.  You can read more about how to clean aircon filters.

Checking Refrigerant Levels.

Low refrigerant levels can causes the AC evaporator coil to freeze.  This is a complex issue and requires a fully licenced HVAC technician to handle the refrigerant and testing.

Adjusting AC Unit Positioning.

Ensure your unit is level.  For split systems, check the indoor unit alignment.  DO NOT ADJUST – contact a professional if it appears unlevel.  For window units, a slight tilt towards the outside helps drainage.

Repairing the Drain Pan.

Inspect the drain pan for damage.  Small cracks may be sealed with epoxy or waterproof sealant.   Allow to dry before use the air conditioner (24-48 hours).  For larger issues, replacement of the drain pan may be recommended.  If the drain pan is sold as part of the whole indoor unit chassis, replacement of the whole system is typically recommended.

Inspecting Condensate Pump (if applicable).

If your AC unit has a pump, ensure it’s functioning correctly.  A faulty pump can cause water to overflow from the pan, thus dripping at the indoor unit.  Drain pumps should be serviced more frequently than even air conditioning units.

Regular Maintenance Check

Complete your home air conditioner service checks on a regular basis.  Then engage a professional for annual maintenance at a minimum.  They can inspect and clean components that are hard to reach or require specialised knowledge and licencing.

Remember, safety first!  Always disconnect and/or isolate power to your AC unit before attempting any repairs or maintenance.  If you’re unsure or the problem persists, it’s best to call a professional HVAC technician.


Commercial air conditioning service technician brisbane


Is water dripping from AC dangerous?

Yes and no – it all depends on what you consider dangerous.  Leaking water from an air conditioner can certainly pose several risks that shouldn’t be overlooked.

Mould and Mildew Growth

Persistent dampness from an AC water leak can create the ideal environment for mould and mildew.  This can cause health issues, especially for those with allergies or asthma.

Property Damage

Water can damage ceilings, walls, floors, and furniture.  Over time, this can lead to structural issues, especially if the leak is not addressed promptly and professionally.

Electrical Hazards

Water and electricity do not mix.  In fact, they are a dangerous mix.  Leaks can cause short circuits in the air conditioner unit and/or other nearby electrical appliances.  This also poses a fire risk.

Slip Hazard

Water dripping from an AC indoor unit can create slippery surfaces.  This creates a slip hazard, leading to potential falls and injuries.

Air Quality Issues

Besides mould, excessive moisture can affect indoor air quality (IAQ).  This makes the indoor environment uncomfortable or unhealthy.  This is a particularly serious issue in the workplace with commercial air conditioning.

To manage and mitigate these risks, it’s important to address indoor air conditioning water leaks immediately.  Regular maintenance is key, with a mix of DIY and professional HVAC assistance.

Despite all the best efforts, there are still some water leak issues that cannot be prevented.  This is where rapid responds from a local air conditioning company comes in.

Need urgent assistance to fix an air conditioner leaking water inside?  Book your local HVAC technician for air conditioning repair or service today.