Why Is My AC Leaking Water? Common Causes and What to Do

🌬️ First, Is It Normal for an AC to Produce Water?

Yes — but only inside the system, not on your floor.

As your air conditioner pulls humidity from the air, moisture condenses on the evaporator coil and drips into a drain pan, then flows out of your home through a condensate drain line. If any part of this process is disrupted, water may leak or overflow, potentially causing water damage, mold, or system failure.

🔍 Six Common Reasons Your AC May Be Leaking Water

1. Clogged Condensate Drain Line

Over time, dust, algae, and mold can accumulate inside the drain line, preventing water from draining correctly. This causes the drain pan to fill and overflow.

📍 This is one of the most common AC issues during humid St. Louis summers.

2. Dirty or Blocked Air Filter

A clogged air filter restricts airflow, which can cause the evaporator coil to get too cold and freeze over. When it melts, excess water can overwhelm the drain pan and leak out.

💡 Regular filter changes help prevent this and improve system efficiency.

3. Low Refrigerant Levels

Low refrigerant can also lead to frozen coils. This typically results in both poor cooling performance and unexpected water leakage once the coil thaws.

🚨 Low refrigerant often signals a leak and should always be handled by a licensed HVAC technician.

4. Cracked or Rusted Drain Pans

Older systems (especially those over 10 years old) may have a corroded or cracked drain pan that can’t correctly hold water, leading to leaks.

🔧 This is usually an easy fix, but it does require inspection and replacement of the part.

5. Improper Installation or Uneven Unit Positioning

If your AC unit wasn’t installed level, water may pool in the wrong areas or fail to drain altogether. Even a slight tilt can lead to a persistent leak.

📏 This is especially important in new construction or after recent AC installations.

6. Excess Humidity or Oversized Unit

In some cases, high humidity or an oversized unit that short-cycles can create more condensation than your system is designed to handle, resulting in overflows or leaks.

🌡️ This is one reason why system sizing and home humidity control are so important.

✅ What You Can Do Next

If you notice your AC leaking water, don’t panic — but don’t ignore it either.

📞 Call a trusted HVAC professional to diagnose the issue and perform any needed repairs. At Thomas Hoffmann Air Conditioning & Heating, our expert technicians provide fast, honest, and thorough service to homes across St. Louis.

We’ll:

• Inspect your drain line, coil, and refrigerant levels
• Clean or repair any clogged or damaged components
• Ensure your system is running safely and efficiently

🧰 Prevent Future AC Leaks With Regular Maintenance

The best way to avoid mid-summer breakdowns or water damage? Schedule a seasonal AC tune-up. Routine maintenance helps catch small problems — such as clogs, corrosion, or low refrigerant levels — before they cause serious issues.

🗓️ We recommend booking a spring or early summer inspection to keep your system leak-free and ready for the St. Louis heat.