How an aircon is meant to handle water
Your aircon pulls humidity out of the air in your home. That moisture condenses on the cold indoor coil, drips down into a small drain pan, and runs out a thin pipe to the outside of the house. When it's all working, you never see a drop inside. When something blocks that path, the water has to go somewhere — and "somewhere" ends up being your floor, wall or the indoor unit itself.
The five reasons it's dripping inside
1. A blocked drain line — by far the most common
This is the cause we see more than all the others put together. That thin drain pipe clogs with dust, grime and mould over a year of running, and once it's blocked the water backs up into the drain pan and overflows.
How to spot it: find the drain pipe outside (a small white or grey pipe, about pencil-thick). If no water is trickling out of it while the aircon's running, it's blocked.
DIY fix (about 10 minutes): hold a wet/dry vacuum over the outdoor end of the drain pipe and run it for 60–90 seconds. With luck it sucks the blockage straight out. A fully set mould plug won't budge this way — those need a proper flush.
2. A filthy filter
A clogged filter starves the unit of airflow, the coil gets too cold, ice forms, and when it melts it overflows the pan. Filters are meant to be cleaned monthly; most homes up here do it once in a blue moon.
DIY fix: pop the front cover, slide out the mesh filters, vacuum then rinse them with mild soapy water, let them dry fully and refit. If the leak stops within an hour, that was your problem.
3. A frozen indoor coil
Caused by low refrigerant (a gas leak — that's a tech job), restricted airflow from a dirty filter, or running the unit very cold for hours. The coil ices over, then melts and floods the pan.
How to spot it: turn the unit off, open the front cover, and look for white ice on the coil. If it's there, leave the unit off for a few hours to thaw, then run it on Fan mode for half an hour to dry out before you test it again.
4. A cracked or rusted drain pan
On older units — ten years and up — the drain pan can rust through or crack, so the water bypasses it entirely and drips onto the wall or ceiling.
DIY fix: none — this one needs a tech to assess and replace.
5. Not enough fall on the drain line
If the unit or the drain line was installed dead level, the water has nowhere to flow. It needs a slight downhill run. Rare in an established home, but it turns up after a reno or a DIY install.
DIY fix: none — the drain line geometry has to be corrected.
Why it happens up here in the dry tropics
Townsville and Mackay are dry for most of the year, so the drain line spends the dry season slowly packing up with dust and grime. Then the wet hits — roughly January to March — and the air turns humid, so the aircon runs flat out and pulls far more water out of the air than it does the rest of the year. That's the moment a line that's been quietly clogging finally backs up. It's why indoor leaks are our number-one service call over summer, and why clearing the line before the wet is the smart move.
Drain flush + deep clean
From $89/unit on the Standard Clean (filter clean, coil rinse, drain check, system test). The Premium Deep Clean — the recommended fix for a real drain-line clog — is $189/unit and covers the full chemical wash: barrel pull, coil wash, drain pan and line flush, and a straight answer on whether the leak's sorted. No call-out fee.
When to call us
- You tried the vacuum on the drain line and it's still leaking.
- You can see ice on the indoor coil that doesn't clear with the unit off.
- The unit's older than about eight years and the drain pan looks rusty.
- It smells musty or mouldy when it runs.
The honest answer
Nine times in ten, a dripping aircon is a blocked drain line and you can clear it yourself with a vacuum in ten minutes. The rest — a frozen coil, a cracked pan, a gas leak — needs a tech. We'll come out, diagnose for free, and tell you straight whether it's a job you can do yourself or one worth our time. No upselling. That's the only way we know how to do this.