Why Is My Air Conditioner Leaking Water?

When homeowners notice water pooling around their AC, the first reaction is usually

concern—and for good reason. A leaking air conditioner can lead to damaged flooring, mold growth, and poor system performance if the cause isn’t addressed quickly. From a technician’s standpoint, water leaks are often a symptom of an underlying issue within the drainage, airflow, or refrigeration process. Understanding what’s happening inside your system can help you respond sooner and avoid costly repairs. Below are the most common causes of an AC leaking water and what they mean for your system.

Common Causes of Air Conditioner Leaks

1. Clogged or Backed-Up Condensate Drain Line

This is the most frequent cause of water leaks. Dirt, dust, algae, and microbial growth can obstruct the drain line, preventing proper condensate flow. When the line is blocked, water backs up into the evaporator pan and eventually overflows. As technicians, we clear the line, flush it, and ensure proper slope to prevent recurring blockages.

Pro Tip: Many of these clogs can be avoided with routine system upkeep. If you

haven’t already, check out our guide on Maintaining HVAC Coils, Drain Lines & Air

Filters to help prevent issues like this from developing.

2. Damaged or Corroded Drain Pan

On older systems—typically 10+ years—the evaporator drain pan can rust, corrode, or develop cracks. Once compromised, the pan can no longer hold condensate, causing water to drip directly into surrounding areas. Replacement is usually the best solution and can also indicate that the system is reaching the end of its lifespan.

3. Frozen Evaporator Coils

When airflow is restricted or refrigerant levels are incorrect, the evaporator coil can freeze. As the ice melts, the excess water overwhelms the drain system, leading to leaks. Coil freezing is often caused by:

● Dirty or restrictive air filters

● Blocked vents or duct issues

● Refrigerant leaks

● Faulty blower motors

A technician needs to identify the root cause to prevent future freeze-ups.

4. Low Refrigerant Levels

Low refrigerant causes the evaporator coil to operate below freezing temperature. Ice forms, then melts, resulting in water leaks. Because refrigerant doesn’t get “used up,” low levels always indicate a leak somewhere in the system. A licensed HVAC tech must locate and repair the leak before recharging the system.

5. Improper Installation or Incorrect Leveling

If the air handler isn’t installed with the proper pitch, or if the condensate line lacks correct slope, water won’t drain efficiently. In ductless mini split systems, improper leveling of the indoor unit can also cause internal water to spill over the drain trough. Correct installation prevents these issues entirely.

6. Excess Condensation from High Humidity

During extremely humid weather, your AC produces more condensation. If the drain line is partially clogged, the drain pan is undersized, or the system is mismatched to the home’s cooling load, excess water may overflow. While some moisture is normal, repeated leaking during humidity spikes usually signals drainage issues.

7. Faulty or Overwhelmed Condensate Pump

Homes with air handlers installed below grade often rely on a condensate pump. If the pump fails, becomes clogged, or loses power, condensate has nowhere to go and will leak around the unit. Routine pump tests ensure proper operation, especially during peak cooling season.

When to Call an HVAC Professional

Some homeowners may be able to check a clogged air filter or identify visible debris around the drain line, but most AC leaks require professional diagnosis. You should reach out to a licensed HVAC technician if you notice:

● Water pooling around your air handler or mini split head

● Ice forming on your refrigerant lines or evaporator coil

● A musty odor from stagnant or standing water

● Drain line clogs that keep returning

● Reduced airflow or system performance

Prompt attention prevents water damage, mold growth, and avoidable repairs. If you suspect something is wrong with your system—even if the leak seems minor—contact Dezier Air. Our technicians can quickly diagnose the issue, restore proper drainage, and ensure your air conditioner is running efficiently and safely.