Why Is My Mini Split Leaking Water?

A ductless mini-split system can be a great heating and cooling solution. They’re well-known for their energy efficiency. The majority of the time, they operate without a hitch. However, occasionally, you may ask “Why is my mini-split dripping water?”

The answer depends on the cause. Let’s take a look.

A mini-split AC leaking water is not an uncommon occurrence. A mini-split should not leak water during heat mode. That’s because a mini-split air conditioner or heating and cooling unit produces condensation during the cooling cycle, but not during heat mode.

There are several main causes for a mini-split dripping water:

• Dirty filter
• Clogged drain line
• Damaged drain pan
• Refrigerant leak
• Improper installation

Like any HVAC system, a mini-split HVAC system has air filters. If the filters become severely clogged, they can restrict airflow and cause a frozen evaporator coil. A frozen coil will eventually drip. Running the system with a frozen coil can damage the system. Turn it off and let the coil thaw out. Have towels or a bucket on hand.

The fix: Clean the air filters regularly. In all the mini-splits you have.

We mentioned that during the cooling process, mini-splits produce condensation. These water droplets then flow down into the drain pan and then into the condensate drain line or PVC pipe and drain outside your home. However, sometimes the drain line can get clogged, causing the water to back up into the unit and start dripping out of the unit and onto the wall or floor.

The fix: Clear the blocked drain line, and replace it if it is cracked.

The drain pan collects the water that condenses on the evaporator coil. In older mini-split units, the drain pan may rust or crack, causing the mini-split to leak water.

The fix: Have an HVAC professional service the unit and replace the drain pan.

It is also possible that your mini-split is leaking water because of refrigerant issues. If your mini-split air conditioning and heating system is operating with low refrigerant levels, it can cause the aforementioned frozen evaporator coil.

The fix: If you suspect a refrigerant leak, schedule mini-split repair. A technician will check the refrigerant levels and refrigerant lines and propose a fix.

While an HVAC professional could be to blame for improper installation, this is more common in DIY installations. An inexperienced installer may not mount the unit correctly or achieve the proper slope for proper drainage. If the indoor unit is tilted forward, it can cause water to overflow and drip or come out through the air vents.

The fix: Call an HVAC professional to troubleshoot and fix the problem.

If your unit is still under warranty, you should have an HVAC professional dismantle the unit and clear the condensate line and drain pan for you. Call your mini-split installer if the system was installed recently. Some DIY maintenance and repairs can void the warranty. We would recommend an HVAC service call even if the indoor unit is out of warranty.

The drain line must be connected just right to ensure proper drainage. The fittings may be bad or you may need a new drain line or drain pan. An HVAC technician can also spot other issues with your system and fix them all at once.

Take care of your ductless mini-split system to help prevent problems. Clean the reusable mini-split filters on each indoor ductless unit regularly to help prevent problems with your ductless HVAC system. Whether you have one or multiple AC mini-splits or a multi-zone mini-split heating and cooling system, make filter maintenance a part of your household routine.

Why? Because clogged or dirty filters can cause a lot of different problems, including

• Water leaks
• Mold and mildew
• Musty smell
• Poor or no cooling
• Poor or no heating
• System damage

Other DIY maintenance includes keeping the outdoor mini-split heat pump clear. Plant debris, snowdrifts, and shrubbery can restrict airflow. Trim shrubbery or other plants to keep them at least two feet away from the outdoor unit.  Clear snow away from the unit as well.

Schedule professional mini-split maintenance twice a year for a ductless mini-split heating and cooling system - once before the cooling season and once before the heating season. Once a year may suffice for a cooling-only system.

If your system is still under warranty, we recommend scheduling with the mini-split installer you used. For best results, work with an HVAC company that has extensive experience with ductless mini-split heating and cooling systems.

During the maintenance visit, the HVAC technician should:

• Thoroughly inspect and clean the system including:
  • Outdoor ductless heat pump
  • Indoor mini-split units
  • Condensate drain line

• Ensure the ductless system operates effectively.
• Check for refrigerant leaks.
• Check electrical connections.
• Make minor repairs.

Consider signing up for a service plan and the company will contact you when it’s time for a maintenance visit.

Anne Fonda, Content Writer at Trane Technologies

A Content Writer with Trane Technologies, Anne Fonda researches topics and writes for Trane® and associated residential HVAC brands. She works in collaboration with Trane Technologies subject matter experts, offering easy-to-understand, informative content on complex topics. Her goal is to help consumers make informed decisions on the products and services they need.

She has written for HVAC and other service provider websites for over 16 years. Before transitioning to web content writing, Anne had a 14-year stint as an award-winning journalist. She graduated cum laude from the University of Missouri-Columbia School of Journalism. When she’s not working, Anne enjoys playing word games, reading, gardening, spending time with family, and visiting gardens and museums.

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