A split or ducted air conditioner dripping water indoors is one of the most common aircon complaints Brisbane homeowners raise, especially through the humid summer months. Some causes are a quick fix; others point to a bigger problem that’s worth having looked at before it causes water damage to ceilings, walls or flooring. Here’s what’s usually behind it.
Blocked or Dirty Condensate Drain
Every air conditioner produces condensate as it cools and dehumidifies the air, and that water is meant to run away through a drain line to the outside. In Brisbane’s humidity, algae, dust and debris build up inside that drain line faster than in drier climates, and once it’s partially blocked the condensate tray overflows and drips back into the house — usually from the indoor unit or through the ceiling for a ducted system. This is by far the most common cause of an internal water leak and is usually straightforward to clear.
Incorrect Installation Fall or a Blocked Drain Pump
Condensate lines rely on a consistent downward fall to drain properly by gravity, and if a line was installed with a sag or insufficient fall — common with older installs or awkward ceiling spaces — water can pool and back up even when the line isn’t blocked. Some ducted systems use a small drain pump where gravity drainage isn’t possible; if that pump fails, the same overflow and leak symptoms show up.
Low Refrigerant (Gas) Causing Ice Build-Up
If refrigerant has leaked and is running low, the indoor coil can ice up rather than just condensing water normally. When the unit is switched off, or the ice melts faster than it forms, that extra meltwater often overwhelms the drain tray and leaks well beyond what a normal condensate drain is designed to handle. A system that’s iced up, blowing warm air, or short-cycling alongside a leak usually needs a proper regas rather than just a drain clean.
Dirty or Blocked Air Filters
Restricted airflow from a dirty filter reduces how well the coil can absorb heat, which can also lead to icing and the same overflow problem described above. This is one of the easiest causes to prevent with regular filter cleaning, particularly during high-use summer months.
Outdoor Unit Leaking or Pooling Water
Some water pooling around the outdoor condenser unit during or after operation is completely normal, especially in humid weather or during defrost cycles on reverse-cycle systems in winter. It only needs attention if it’s excessive, running toward the house foundations, or the unit is sitting on an uneven or failing base.
Why You Shouldn’t Ignore It
- Ceiling stains and sagging plasterboard from a slow ducted-system leak
- Mould growth in ceiling cavities and around vents from ongoing moisture
- Damage to flooring, skirting or cabinetry below a leaking split system
- A leak that’s a symptom of low gas, which will keep getting worse and cost more to fix the longer it’s left
What a Service Call Involves
A proper leak diagnosis includes checking and flushing the condensate line, confirming the drain fall or pump is working, checking refrigerant pressures, and inspecting the filter and coil. Most condensate-drain leaks are resolved in a single visit; refrigerant leaks need locating and sealing before a regas, since simply topping up gas without finding the leak just means doing it again in a few months.
Aircon Leak Repairs Across Brisbane
Integrated Trade Services services and repairs split system and ducted air conditioners across Brisbane and Moreton Bay, including condensate drain clears, regas and leak detection. If your system is dripping water inside or outside, get in touch for a service booking, or see our full air conditioning services in Brisbane.
Related guides
- Air conditioner not cooling? Common causes
- How often should you service your air conditioner?
- Musty smell from your air conditioner? What it means
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