Short answer: Most indoor AC leaks come from a clogged condensate drain line, a cracked drain pan or a frozen coil. Turn the system off, dry the area, and check the drain line and filter.
An air conditioner pulls moisture out of the air and drains it away. When that water has nowhere to go, it ends up on your ceiling, floor or walls.
Common causes
- A clogged condensate drain line, the most common cause
- A rusted or cracked drain pan
- A dirty filter that lets the coil freeze, then melt
- A broken condensate pump
- Low refrigerant that makes the coil ice up
What you can check
- Turn the AC off at the thermostat
- Dry the area and move belongings
- Replace the air filter if it is dirty
- Find the drain line where it exits outside and look for a blockage
- Look at the drain pan under the indoor unit for water or cracks
If the unit is in the attic
A leak from an attic unit can soak insulation and ceilings quickly. Many attic units have a secondary pan and a float switch that shuts the system off when water rises. If your AC stopped and there is water in the pan, that is likely what happened.
Watch for damage
- Brown stains on the ceiling below the unit
- Sagging drywall
- A musty smell, which can mean mold
When to call a professional
Call an HVAC technician if the drain line will not clear, the coil is icing, or the leak keeps coming back. If water soaked the ceiling or walls, a water damage company can dry it properly.
Frequently asked questions
Can I still run the AC while it leaks?
It is better not to. Water can damage ceilings and the unit itself.
How often should the drain line be cleaned?
Once or twice a year, often during a spring tune up.
Is it normal to see water outside?
Yes. Water dripping from the drain line outside is normal when the AC runs.
Related
Read our AC repair page and our AC freezing up guide.
For more background, see the U.S. Department of Energy Energy Saver site, and if you need help, Sifixit can connect you with a local provider.
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