Troubleshooting

Why Is My Window AC Leaking Water Inside My Miami Home?

By Miami Window AC Pros · November 2025 · 4 min read

A leaking window AC can damage floors and walls and cause mold within 48 hours in Miami's humidity. Here are the 5 most common causes and what to do about each.

Act Quickly: In Miami's humidity, water damage leads to mold within 24–48 hours. Don't ignore it.

Why Window ACs Produce Water

Your AC removes humidity from the air as it cools. This condensate water should drip out the back (outside). When it ends up inside, something has gone wrong.

The 5 Most Common Causes

Cause 1

Clogged Drain Pan or Drain Hole

The drain pan channels water out through a small hole. In Miami, this hole gets blocked by algae, mold, or debris quickly.

DIY Fix: Unplug the unit, clear the drain hole with a wire or compressed air, and flush with diluted white vinegar to kill mold.

Cause 2

Improper Tilt (Level or Tilted Inward)

Window ACs need a slight backward tilt (~½ inch down toward outside) so gravity directs water to the drain. A level or inward-tilted unit sends water into the room.

DIY Fix: Check with a level. Add shims or adjust the window bracket so the unit tilts slightly outward.

Cause 3

Frozen Evaporator Coils Melting

Restricted airflow (usually from a clogged filter) causes the evaporator coil to freeze. When the unit cycles off, ice melts rapidly and overwhelms the drain pan.

DIY Fix: Switch to "fan only" for 2–3 hours to defrost, then clean the filter. If freezing recurs, call a pro — it may indicate a refrigerant issue.

Cause 4

Dirty or Clogged Air Filter

Miami's dust, pollen, and salt air clog filters faster than anywhere. A blocked filter causes freezing → water overflow. Clean it every 2–3 weeks during peak season.

DIY Fix: See our full filter cleaning guide.

Cause 5

Cracked or Rusted Drain Pan

Units 7+ years old in Miami's coastal salt air can develop cracks or rust holes in the drain pan itself. Common in Miami Beach, Key Biscayne, and Coconut Grove homes.

Fix: Temporary epoxy patch, but usually signals it's time to evaluate repair vs replacement.

When to Call a Professional

  • You've cleaned the filter and drain, corrected the tilt, but it's still leaking
  • Coils keep freezing even after filter cleaning
  • Water is coming from multiple locations on the unit
  • You can see mold growth inside the unit
  • There's an oily residue or hissing sound (refrigerant leak)
"In Miami, we see three water leak calls for every other service call. The humidity here is unforgiving — preventive maintenance is the only real solution." — Miami Window AC Pros

AC Still Leaking After These Fixes?

Call us for same-day diagnosis. Flat-rate quote before any work begins.

Call 877-388-2317