You notice the drip before you notice anything else – a damp patch on the wall, water under the indoor unit, or a slow trickle running where it definitely should not be. If you’re asking why is my aircon leaking, the short answer is that something is stopping moisture from draining the way it should. The longer answer depends on the system, the installation, and how long the problem has been building.
Air conditioners naturally produce water as they remove humidity from the air. In normal operation, that condensation collects, runs into a drain tray and flows away through a drain line. When any part of that process is blocked, damaged or poorly set up, water ends up where it shouldn’t. Sometimes it is a simple maintenance issue. Other times, it points to a fault that needs proper repair before it causes damage to plaster, flooring, cabinetry or the unit itself.
Why is my aircon leaking from the indoor unit?
When water is leaking from the indoor unit, the most common culprit is a blocked condensate drain. Dust, grime, mould and debris can build up in the drain line over time, especially if the system has not been serviced regularly. Once that line starts backing up, the tray overflows and the water finds the easiest path out – often down the wall or straight onto the floor.
A dirty filter can also trigger leaks, even though it seems unrelated at first glance. If airflow is restricted, the evaporator coil can become too cold and start to ice up. When that ice melts, it can produce more water than the tray and drain can manage, especially if there is already a partial blockage. This is one of those issues that starts small and then gets worse quickly in heavy use periods like summer.
Another possibility is that the drain tray itself is cracked, rusted or out of position. Older systems are more prone to this, but we also see it in units that have been poorly installed or knocked during previous work. If the tray cannot catch and direct condensation properly, leaking is almost inevitable.
Installation quality matters as well. A split system indoor head needs to be mounted at the correct angle so condensation flows toward the drain point. If the unit is not level, or the pipework has been run with the wrong fall, water may pool instead of draining away. This is not always obvious from the outside, which is why leaks that keep returning often need a proper inspection rather than another quick clean.
Common reasons your aircon starts leaking
There is no single answer to why my aircon is leaking because a few different faults can produce the same symptom. The key is working out whether the leak is being caused by maintenance, wear and tear, or a system fault.
Low refrigerant is one example. When refrigerant levels drop due to a leak elsewhere in the system, pressure changes can make the coil run too cold, leading to icing. Once the ice melts, you can end up with excess water around the indoor unit. In this case, wiping up the leak does nothing to fix the actual problem.
A damaged or disconnected drain line is another common cause. Over time, pipework can deteriorate, sag, crack or become loose at a connection point. In roof spaces and tight wall cavities, this can go unnoticed for quite a while. By the time you see visible water indoors, the leak may have already been affecting surrounding materials.
In ducted systems, leaks can also come from blocked drains, faulty pumps or issues around the indoor fan coil unit, which is often hidden in the ceiling. Because the components are less visible, homeowners usually notice the symptoms first – stains, drips or musty smells – rather than the cause itself.
Then there are the weather-related scenarios. On very humid days, your system can produce a lot more condensation than usual. A properly working system should still handle that, but if there is already a minor blockage or drainage issue, high humidity can tip it over into a visible leak.
What you can safely check yourself
There are a few practical things you can look at before calling in a technician, as long as you keep it simple and safe.
Start with the filter. If it is loaded with dust, remove it, clean it according to the manufacturer’s instructions and let it dry fully before refitting. A clean filter improves airflow and can sometimes stop icing-related leaks from returning.
Next, look for obvious signs of trouble around the indoor unit. If you can see water pooling, staining on the wall, or dripping from one side more than the other, that is useful information to pass on when booking a service. If the leak started after the unit was heavily used for several days, or after a period of extreme humidity, mention that too.
You can also check whether the system is set extremely low for long periods. Running a unit flat out at a very low temperature does not always cause leaks on its own, but it can contribute to icing if there are existing airflow or refrigerant issues.
What you should not do is start pulling covers off, poking into the drain with makeshift tools, or trying to regas the unit. Air conditioning systems need to be handled properly, and guessing can turn a manageable repair into a bigger one.
Signs the problem needs professional attention
If the leak keeps coming back after cleaning the filter, it is time to have it looked at properly. The same goes for any leak that is heavy, causing staining, tripping electrical components, or showing up around a ceiling cassette or ducted system.
A musty smell is another warning sign. Standing water in the tray or drain can lead to mould and bacteria growth, which is not something you want circulating through the home. If the unit is also struggling to cool, freezing up, or making unusual noises, the leak is probably a symptom of a broader system fault.
Water and electrical equipment are not a combination to ignore. If you see water near wiring, power points, light fittings or the outdoor isolator, switch the system off and arrange a licensed technician to inspect it.
For homeowners and property managers, acting early usually means a simpler repair and less chance of damage to paint, gyprock, insulation or timber finishes. That matters even more in well-finished homes where a small internal leak can leave an expensive mark.
Why regular servicing helps prevent leaks
A lot of aircon leaks are preventable. Routine servicing gives a technician the chance to clean the system properly, inspect the drain, check the tray, test performance and pick up issues before they become obvious water damage.
That does not mean every leak comes down to neglect. Some systems develop faults due to age, component failure or original installation problems. But regular maintenance does make it easier to spot those issues early and keep the unit operating the way it should.
For homes across Newcastle and Lake Macquarie, that matters most before the peak heating and cooling seasons. Systems tend to show their weaknesses when they are working hardest, and a partially blocked drain in mild weather can become a full overflow during a humid summer run.
If your system has leaked once before, it is worth taking seriously even if it seems fine now. Water stains dry out. Drain lines partially clear. The symptom disappears, but the cause often remains.
When repair makes sense and when replacement might be better
If your aircon is relatively modern and otherwise performing well, a leak is often straightforward to repair. Cleaning a blocked drain, replacing damaged pipework, correcting the fall, or addressing a refrigerant issue can usually get the system back to normal.
If the system is older, leaking repeatedly and struggling to cool properly, the conversation can shift. At a certain point, repeated repairs on an ageing unit stop being good value. That is especially true if parts are failing, the tray is deteriorated, or the original installation has ongoing drainage issues that were never properly resolved.
An honest technician should tell you which side of that line you are on. Sometimes the best outcome is a repair. Sometimes it is planning a replacement before more money goes into a unit that is near the end of its life.
K&S Air & Electrical takes that approach because most customers are not looking for the fastest sales pitch – they want clear advice, reliable workmanship and a fix that lasts.
If your air conditioner is leaking, the main thing is not to ignore it and hope it sorts itself out. Water around an indoor unit is your system telling you something is off. The sooner it is checked, the better chance you have of avoiding bigger repairs and keeping your home comfortable, clean and protected.