An AC usually leaks water inside because the condensate drain line is clogged, the drain pan is cracked or overflowing, or the evaporator coil froze and is melting. Turn the system off, check the drain pan and the overflow switch, and clear the drain line. A frozen coil or a refrigerant problem needs an HVAC technician.
Key takeaways
- A clogged condensate drain line is the most common cause.
- A dirty air filter can freeze the coil, which then floods the pan as it melts.
- Water dripping from the outdoor drain pipe is normal. Water inside is not.
- In attics, an overflowing pan shows up as a ceiling stain.
Why is my AC leaking water inside the house?
Your air conditioner pulls moisture out of indoor air. That water drips off the cold evaporator coil into a drain pan, then runs out through a small PVC pipe called the condensate drain line. In an Arizona summer, a central AC can produce gallons of water a day. When anything in that path fails, the water ends up in your house.
| Cause | What you'll notice | Who fixes it |
|---|---|---|
| Clogged condensate drain line | Full drain pan, water around the air handler, AC shuts off | Often a homeowner, or an HVAC tech |
| Cracked or rusted drain pan | Water under the air handler even with a clear drain | HVAC technician |
| Dirty air filter | Weak airflow, ice on the coil or lines, then water when it melts | Homeowner (replace filter), then a tech if it keeps freezing |
| Low refrigerant | Ice on copper lines, warm air, then leaking | HVAC technician |
| Failed condensate pump | Water near a small pump box beside the unit | HVAC technician |
| Loose or badly sloped drain line | Leak at a pipe joint or in the ceiling | HVAC technician |
Is it normal for an AC to leak water?
It is normal for water to drip from the end of the condensate drain line outside, often near the foundation or on the roof. That is the system working. It is not normal to see water around the indoor air handler, in a hallway closet, or coming through the ceiling.
How do you unclog an AC drain line?
- Turn the AC off at the thermostat and the breaker.
- Empty the drain pan with a wet vacuum or towels.
- Find the drain line access. Many systems have a T-shaped fitting with a cap near the air handler.
- Clear the clog from outside. Hold a wet/dry vacuum hose tight over the outdoor end of the drain line for a minute or two to pull out algae and sludge.
- Flush the line. Pour about a cup of distilled white vinegar into the access fitting, wait 30 minutes, then follow with water.
- Turn the AC back on and watch for steady drips at the outdoor end.
If the pan fills again within a day, or the line will not clear, call an HVAC technician. Many systems also have a float or overflow switch that shuts the AC off when the pan fills. If your AC keeps shutting off on hot days, that switch may be telling you the drain is blocked.
AC water soaked the ceiling or a closet floor? Get it dried before the drywall gives way.
Call: (856) 481-6893Why do AC leaks happen so often in Arizona?
East Valley air conditioners run for most of the year, and during monsoon season the air holds much more moisture, so systems produce more condensate. Dust storms push fine dirt into filters and drain pans, which feeds the algae that clogs drain lines.
Many homes here put the air handler in the attic. When its pan overflows, water lands on the ceiling drywall below. A small yellow stain under the unit is often the first sign. Our guide to fixing a water-damaged ceiling covers what to do next.
How can you prevent AC water leaks?
- Change the air filter every one to three months, more often during dusty months.
- Flush the drain line with vinegar every few months during cooling season.
- Have the system serviced each spring, before the heavy cooling months.
- Make sure the overflow safety switch works, especially on attic units.
- Place a water sensor in the pan or near the air handler.
If the leak has already wet drywall or flooring, see signs of water damage in walls to judge how far it spread.