January 28, 2026
If you have noticed your air conditioner indoor unit leaking water, it is important not to ignore it. If water leaks from the indoor unit, it usually means there is a problem.
A leaking air conditioner can cause water damage, mould growth, weaker cooling, and costly repairs if not fixed. You can identify many common causes early and fix them before the problem gets worse.
In this guide, we explain why your air conditioner indoor unit is leaking water and when to call a professional.
Indoor air conditioners naturally create condensation while cooling your home. Normally, this moisture drains safely outside through the condensate drain system. When something interrupts this process, it can cause water leakage.
If your indoor ac is leaking water, some causes are simple maintenance issues, while others may require professional repairs.
One of the most common reasons for an air conditioner leaking water indoors is a clogged or dirty air filter.
When something restricts airflow, it can make the evaporator coil too cold and cause it to freeze over. Once the ice melts, excess water can overflow from the drain pan and leak inside your home.
Cleaning or replacing the filter regularly can help prevent this issue. Most homeowners should check filters every three to six months, depending on usage and indoor air quality.
A blocked condensate drain line is another common cause of your air conditioner indoor unit leaking water.
Over time, dirt, dust, mould, insects, or debris can clog the drain line and prevent water from flowing outside properly. When the drain line gets clogged, water flows back into the indoor unit and starts leaking inside your home. Using a wet dry vacuum is a highly effective, recommended method for clearing clogged air conditioning.
If you can safely access the outdoor drain outlet, check whether it is blocked. If something blocks the system or damages the pipework, contact a professional air conditioning technician.
Some air conditioning systems use a condensate pump to move water outside. This helps when gravity drainage is not possible.
If the pump fails, condensation cannot drain properly. Water may leak from the indoor unit and stop it running smoothly.
A professional technician can test the pump and determine whether it needs repair or replacement.
The drain pan collects condensation from the evaporator coil and directs it toward the drain line.
Drain pans can wear out because of age. They also face moisture, temperature changes, and contact with chemicals or debris. The material may weaken and become brittle, leading to cracks, pinholes, or warping.
Metal pans may develop rust or corrosion, while plastic pans can dry out, discolour, and fracture. If these issues progress, the pan may no longer hold water properly and can begin to leak or overflow.
If the pan has damage, water may leak through the bottom of the indoor unit. It may not drain properly.
This issue is more common in older air conditioning systems that have been operating for many years. The simple solution is to replace it.
Improper installation can also lead to indoor leaks.
If you notice that the air conditioning is suddenly leaking, there was a problem with the installation. Contact the installers to come back and fix the issue so the system will continue working.
Your air conditioner indoor unit leaking water, can also be caused by low refrigerant pressure or cause refrigerant leaks.
The system will have low pressure if your air conditioning is low on refrigerant. This can cause the evaporator coil to freeze, just like a dirty air filter. Once the ice melts, excess water may drip from the unit.
A qualified technician should handle refrigerant issues, because the system may have a leak that needs repair.
If you notice your air conditioner indoor unit leaking water, taking quick action can help minimise damage.
Switch the air conditioner off immediately to prevent further leaking and reduce the risk of electrical damage.
Inspect your air filter closely to determine whether it needs cleaning or replacement. Cleaning the filter may improve airflow and help prevent further freezing.
If it is safe to do so, inspect the outdoor drain outlet for obvious blockages or disconnected hoses.
If the leak continues or you suspect a larger issue, arrange a professional inspection. Qualified technicians should always handle problems involving refrigerant, electrical components, frozen coils, or pumps.
If your air conditioner indoor unit is leaking water, Roberts Air Conditioning can find the cause and fix the problem.
Roberts Air Conditioning provides professional air conditioning repairs, servicing, maintenance, and installations for homes and businesses. Whether it is a blocked drain, a frozen coil, or a faulty part, skilled technicians can find the problem. They can then recommend the right solution.
Is it normal for an indoor air conditioner to leak water?
No. Outdoor units often drip water from condensation. Indoor leaks usually mean a problem with drainage, airflow, refrigerant levels, or system parts.
Can I still use my air conditioner if it is leaking water?
Turn off the system until you inspect the issue. Continuing to run the unit may cause further water damage or worsen the problem.
How do I stop my air conditioner from leaking water?
Regular maintenance is key. Cleaning filters, servicing the system annually, and checking for blocked drains can help prevent leaks.
How much does it cost to fix an air conditioner leaking water?
The cost depends on the cause of the leak. Simple issues like blocked drains may be inexpensive to repair, while refrigerant leaks or component replacements may cost more.
Can a dirty filter cause an air conditioner to leak water?
Yes. Dirty filters can restrict airflow, causing evaporator coils to freeze and eventually leak water once the ice melts.
Should I repair or replace my leaking air conditioner?
If the system is older and experiencing ongoing issues, replacement may sometimes be more cost-effective. A qualified technician can assess the condition of the unit and recommend the best option.
