Why does my air conditioner leak water?

The short answer

Your AC removes moisture from the air as it cools, and that water is supposed to drain away quietly — but when something blocks or breaks the drainage path, it leaks into your home instead.

How your AC creates water

Air conditioners don’t just cool air — they also pull humidity out of it. Warm, moist air blows over a cold coil (called the evaporator), and water condenses on it, just like droplets forming on a cold glass on a hot day.

That water normally drips into a drain pan and flows out through a drain line. When everything works, you never notice it. When something goes wrong with that process, water ends up where it shouldn’t.

Common reasons for leaking

  • Clogged drain line — This is the most common cause. Algae, mold, and dust build up inside the line over time and block the water from flowing out.
  • Dirty air filter — A clogged filter restricts airflow, which makes the evaporator coil get too cold and freeze. When the ice melts, it overflows the drain pan.
  • Cracked or rusted drain pan — On older units, the pan that catches water can crack or corrode, letting water drip straight through.
  • Low refrigerant — When refrigerant is low, the coil gets abnormally cold and freezes up, causing the same overflow problem as a dirty filter.
  • Improper installation — If the unit isn’t level or the drain line wasn’t angled correctly, water can pool instead of draining.

How to fix it

Start with the easiest fixes first:

  1. Check your air filter — Replace it if it looks dirty. This alone solves many leaking issues.
  2. Clear the drain line — Pour a cup of distilled white vinegar into the drain line opening to break up clogs. You can also use a wet/dry vacuum on the outside end to suck out blockages.
  3. Inspect the drain pan — Look for visible cracks or rust, especially if your system is over 10 years old.
  4. Make sure the unit is level — Use a level to check, and adjust if needed.

When should you worry?

  • Ice on the coil or refrigerant lines — This usually means low refrigerant, which requires a professional.
  • Water near electrical components — Turn the system off and call a technician.
  • Leaking continues after cleaning the drain — There may be a deeper issue with the installation or internal components.

A small amount of water around an outdoor unit is completely normal. Indoor leaking, however, always means something needs attention.

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