Why Is My AC Leaking Water? Causes and What to Do
Water under the indoor unit, a wet ceiling below an attic system, or a puddle by the furnace closet: an AC leak can damage drywall and floors fast. Here are the common causes, what you can safely check, and when to call.
Why your AC makes water at all
Your AC pulls humidity out of the air. That moisture collects on the cold indoor coil, drips into a drain pan and runs out through a condensate drain line. In humid San Antonio summers that can be several gallons a day. A leak means the water is not getting out the way it should.
The most common causes
- Clogged condensate drain line. Algae, dirt and sludge build up and the water backs up. This is the most common cause.
- Frozen coil. A dirty filter, low airflow or low refrigerant can freeze the coil. When the ice melts, it overflows the pan. See ice on your AC is never normal.
- Dirty air filter. It chokes airflow and can lead to a frozen coil.
- Cracked or rusted drain pan. Older pans can leak at the seams.
- Failed condensate pump. Some systems pump the water out. If the pump fails, water backs up.
- Tripped float switch. Many attic systems have a safety switch that shuts the AC off when water backs up. If your AC stopped and there is water in the pan, that may be why.
What to do right now
- Turn the system off at the thermostat to stop more water from forming.
- Protect the area: towels, a bucket, and move anything valuable away.
- Check the air filter and replace it if it is dirty. See how to change your air filter.
- Look for ice on the copper lines or coil. If you see ice, leave the AC off (fan only can help it thaw) and call.
- Check the secondary pan under an attic unit. Standing water there means the main drain is blocked.
- Look at the drain line outside where it exits the house. If it is not dripping while the AC runs, it may be clogged.
Attic units in San Antonio homes
Many San Antonio homes have the AC air handler or furnace in the attic. A leak there shows up as a water stain on the ceiling below. Do not wait on that: wet insulation and drywall can sag and grow mold. Turn the system off and call.
When to call a technician
- Water keeps coming back after you change the filter.
- You see ice on the lines or coil.
- The AC shut off and will not restart (often the float switch).
- There is a ceiling stain, sagging drywall or water near electrical parts.
- The drain pan is cracked or rusted through.
Cowboy's answers 24/7 with our own dispatch on Blanco Road, and you get the price in writing before work starts. See AC repair in San Antonio or our 24/7 emergency HVAC service.
Frequently asked questions
Why is my AC leaking water inside the house?
The most common cause is a clogged condensate drain line. A frozen coil, a dirty filter, a cracked drain pan or a failed condensate pump can also cause leaks.
Is an AC leaking water an emergency?
It can be. Turn the AC off and protect the area. If water is near electrical parts, the ceiling is stained or sagging, or the leak keeps coming back, call for service.
Can I keep running my AC if it is leaking water?
It is better not to. Running it adds more water and can cause ceiling or floor damage, and a frozen coil can damage the compressor.
How do I unclog my AC drain line?
Some homeowners can clear the outside end of the line, but clogs often sit deeper in the line or trap. A technician can clear and flush it and check the pan and float switch.
Why did my AC stop working and there is water in the pan?
Many systems have a float switch that shuts the AC off when water backs up, to prevent a flood. Clearing the drain usually fixes it.
Related service: AC repair in San Antonio · 24/7 emergency HVAC · all heating and cooling services. Cowboy's AC answers 24/7 at (210) 495-7771.
