What to Do If Your AC Unit Is Leaking Water After a Power Outage in St. Louis

If your AC unit is leaking water after a power outage, first turn off the system at both the thermostat and the breaker, then clear the condensate drain line and check the drain pan for blockages or damage. Clean or replace the air filter, restore power, and if the leak continues, contact a professional HVAC technician.

 

Immediate Steps to Stop the Leak

 

• Switch off the AC at the thermostat and locate the circuit breaker to cut all power to the unit.
• Lay absorbent towels or a shallow pan beneath the indoor unit to catch dripping water.
• Inspect the condensate drain line for visible blockages or standing water.

 

Understanding Why Your AC Leaks After a Power Outage

 

When the power goes out and comes back on, your air conditioner can develop leaks because:

• The condensate pump or drain line may lose its prime, allowing water to back up.
• A dirty air filter can cause the evaporator coil to freeze and, upon thawing, produce excess water.
• Safety devices like float switches can trip or malfunction, shutting off drainage.
• The internal drip pan can crack or rust over time, unnoticed until water pools.

 

Checking and Clearing the Condensate Drain Line

 

• Locate the PVC drain line near the indoor coil. It often has a small rubber cap or T-shaped vent.
• Remove the cap and gently insert a wet/dry vacuum to suck out debris or algae.
• Flush the line with a mixture of warm water and a teaspoon of mild dish soap or a cup of white vinegar to kill mold and buildup.
• Replace the cap securely to prevent air leaks.

 

Inspecting and Cleaning the Drain Pan

 

• Slide the indoor unit’s access panel off to expose the metal or plastic pan beneath the coils.
• Check for cracks, rust, or holes and replace the pan if it’s damaged.
• Clean the pan with a solution of warm water and dish soap, scrubbing gently to remove grime.
• Ensure the pan sits level so water flows toward the drain outlet.

 

Replacing or Cleaning the Air Filter

 

• Locate the filter slot at the return-air grille or inside the indoor unit housing.
• Remove the filter and inspect for dirt, pet hair, and dust buildup.
• If reusable, rinse it with water and let it dry completely before reinstalling.
• If disposable, install a new filter matching your system’s size and MERV rating.

 

Restoring Power and Testing

 

• Turn the circuit breaker and thermostat back on.
• Set the thermostat to cooling mode at a temperature lower than the room to start the compressor.
• Observe the unit for at least 15–20 minutes to ensure no further dripping occurs.
• If water still pools, turn off the system immediately to prevent damage.

 

When to Call a Professional HVAC Technician

 

• If you find a cracked drain pan or damaged drain line that you can’t fix yourself.
• When the condensate pump doesn’t run or hum, indicating electrical or mechanical failure.
• If the leak persists after cleaning and filter replacement.
• For annual maintenance to prevent future leaks and ensure efficient operation.

 

Applicability in Different Regions

 

These troubleshooting steps work for homeowners in areas with humid climates and sudden outages, including those in St. Louis and Nashville, where prompt attention can save your home from water damage and restore comfort quickly.