If your air conditioner is leaking water inside, the most common cause is a blocked condensate drain line — turn the unit off, check the air filters, and have the drain line cleared. Your air conditioner constantly removes humidity from the air, and that water is meant to drain outside. When the drain clogs or the filter is dirty, water backs up and overflows from the indoor unit. Here is what causes it and how to fix it.
Common Causes of an Air Conditioner Leaking Water
1. Blocked Condensate Drain Line
This is the number-one cause. Over time the drain line fills with dust, mould and algae. Once it clogs, the water the unit removes from the air has nowhere to go and overflows from the indoor unit. Clearing the drain line is a routine part of a professional service.
2. Dirty Air Filter
A clogged filter restricts airflow and can freeze the evaporator coil. When that ice melts, it produces more water than the drain pan can cope with, and the unit overflows. Clean your filters every 4 to 6 weeks during heavy use to prevent it.
3. Cracked or Overflowing Drain Pan
The drain pan sits under the indoor unit to catch condensation. If it is cracked, rusted or misaligned, water escapes instead of draining away. A technician can replace or reseat the pan.
4. Unit Not Level
If the indoor unit was installed off-level, water pools on the wrong side of the drain pan and drips down the wall instead of flowing to the drain. This is an installation fault that needs correcting by a licensed installer.
5. Low Refrigerant
Low refrigerant drops the coil temperature and causes it to freeze, then leak as it thaws. This needs a licensed technician, as refrigerant handling is regulated work in Australia.
What to Do Right Now
- Turn the unit off to prevent water reaching the electronics and to limit ceiling or wall damage
- Wipe up standing water and place a container under the drip
- Check and clean the filters — this fixes the simplest cases
- Do not keep running it if the leak continues — book a technician to clear the drain line
When to Call a Professional
If cleaning the filters doesn’t stop the leak, the drain line, pan or refrigerant is the problem — all of which need a professional. Because a leaking unit sits right beside electrical components, it’s worth acting quickly. Connex Electrical holds both an electrical contractor licence (QLD #92217) and an ARC refrigeration licence (#AU42842), so we can safely diagnose and fix both the electrical and refrigeration sides in one visit.
What Does It Cost to Fix?
| Job | Typical Cost |
|---|---|
| Callout & diagnosis | From $88 |
| Labour (in-visit repairs) | $185/hr |
| Service & clean (incl. drain line clear) | $120 – $250 |
| Drain pan / refrigerant repair | Quoted after diagnosis |
Most leaks are resolved by a professional air conditioning service, which clears the drain line, cleans the filters and coils, and checks the drain pan. Catching it early is far cheaper than repairing a water-damaged ceiling.
Air Conditioning Service & Repair Across North Brisbane
Connex Electrical provides air conditioning service and repair for all brands across Brisbane and North Brisbane. If your unit is leaking, icing or not cooling, our licensed team gets it sorted fast. For related help, see our guides on why your air conditioner is not cooling and how often you should service your air conditioner.
Reviewed by Lee Gundenswager (Lead Electrician, Connex Lic #92217) and Darren Standring (Owner).
Frequently Asked Questions
The most common cause is a blocked condensate drain line. Your air conditioner removes humidity from the air, and that water normally drains outside. When the drain line clogs with dust, mould or algae, the water backs up and overflows from the indoor unit. Other causes are a dirty air filter, a cracked or overflowing drain pan, or the unit not being level.
Turn the unit off to avoid water damage, then check and clean the air filters. If the leak continues, the condensate drain line is likely blocked and needs clearing — a common part of a professional service. Do not keep running a leaking unit, as water can damage the electronics and your ceiling or wall.
Water itself is not dangerous, but a leaking air conditioner sits right next to electrical components, so a leak near wiring is a genuine risk. Water can also cause mould, and damage ceilings, walls and flooring. Switch the unit off and have it inspected rather than letting it keep leaking.
Some water dripping from the outdoor unit is normal, especially in heating mode when the unit defrosts. Water dripping or leaking from the INDOOR unit is not normal and points to a blocked drain line or dirty filters that needs attention.
Clearing a blocked condensate drain is usually resolved in a single visit. A callout and diagnosis starts from $88, with labour at $185 per hour, and a full service and clean — which includes clearing the drain line — costs $120 to $250. Fixing the leak early is far cheaper than repairing water-damaged ceilings or electronics.
Yes. A clogged filter restricts airflow and can cause the evaporator coil to freeze. When that ice melts, it produces more water than the drain pan can handle, and the unit overflows. Cleaning filters every 4 to 6 weeks helps prevent both icing and leaks.
Air conditioner leaking water? Call Connex Electrical on 0474 207 609 or visit our contact page to book a licensed technician across Brisbane and North Brisbane.