Why is My AC Unit Leaking Water?

Finding a puddle of water around your indoor air handler or noticing water dripping from your AC system is a common (and frustrating) problem for homeowners in San Antonio and Lakeway. While it might look alarming, water leaks are usually a sign that something in the system needs attention — and the sooner it’s fixed, the better.

Here’s a clear breakdown of every common reason an air conditioner leaks water, how a professional technician diagnoses the problem, and why calling a trained HVAC pro is almost always the smarter choice.

Common Reasons Your AC Is Leaking Water

1. Clogged Condensate Drain Line This is the most frequent cause. As your AC removes humidity from the air, the moisture drains through a PVC line. Over time, algae, mold, dust, and sludge can clog the line, causing water to back up and overflow.
2. Dirty or Clogged Air Filter A restricted filter reduces airflow across the evaporator coil. This can cause the coil to freeze. When the ice melts, the excess water overwhelms the drain pan and leaks out.
3. Frozen Evaporator Coil Ice builds up on the indoor coil and later melts into a large amount of water. Common triggers include dirty filters, low refrigerant, or restricted airflow.
4. Cracked, Rusted, or Damaged Drain Pan The metal or plastic pan under the evaporator coil can crack, rust, or corrode over time, allowing water to drip directly onto the floor or ceiling.
5. Low Refrigerant When refrigerant levels drop (usually from a leak), the evaporator coil gets too cold and freezes. Melting ice then causes water leaks.
6. Dirty Evaporator Coil A heavily soiled coil reduces heat transfer and can contribute to freezing or improper drainage.
7. Disconnected, Damaged, or Improperly Sloped Drain Line If the drain line has come loose, developed a hole, or doesn’t slope correctly, water cannot flow out of the system.
8. Failed Condensate Pump Some systems (especially those in basements or areas without gravity drainage) use a small pump. When the pump fails, water backs up and leaks.
9. Unlevel Air Handler or Improper Installation If the indoor unit is not level, water may not flow properly into the drain pan or drain line.
10. Secondary Drain or Float Switch Issues Many systems have a secondary drain and safety float switch. Problems with these components can allow water to overflow or fail to shut the system off when needed.

How a Professional Technician Diagnoses an AC Water Leak

A trained HVAC technician follows a systematic process to find the exact cause instead of guessing:

1. Turns off power to the system for safety.
2. Performs a thorough visual inspection of the indoor unit, drain pan, and surrounding area.
3. Checks and replaces the air filter if needed.
4. Inspects the evaporator coil for ice, dirt, or damage.
5. Examines the condensate drain pan for cracks, rust, standing water, or improper installation.
6. Clears and tests the condensate drain line using specialized tools (wet/dry vacuum, nitrogen, or approved cleaning methods).
7. Verifies the drain line has proper slope and secure connections.
8. Tests the condensate pump (if equipped) and float switches.
9. Checks refrigerant pressures and looks for signs of a low charge or leak.
10. Confirms the air handler is level and properly installed.
11. Identifies the root cause and explains repair options clearly before any work begins.

This methodical DIY approach prevents temporary “fixes” that fail a week later.

Why Hiring a Professional Is Far Better Than DIY

Attempting to fix an AC water leak yourself often leads to bigger problems. Homeowners frequently misdiagnose the issue, damage components, or create new leaks while trying to clear a drain line. Working around electrical components, refrigerant lines, and the air handler also carries real safety risks.

A professional brings the right tools, training, and experience to:

• Accurately identify the true cause the first time
• Make lasting repairs instead of temporary patches
• Protect your system’s warranty
• Prevent water damage to ceilings, floors, and walls
• Avoid costly secondary problems caused by incorrect DIY attempts

In the humid climate of San Antonio and Lakeway, even a small water leak can quickly lead to mold growth if left unresolved. Getting it handled correctly protects both your comfort and your home.

Get Help from Air & Plumbing Today

If your AC is leaking water, don’t wait for the problem to get worse. At Air & Plumbing Today, we make it simple and transparent for residential customers in San Antonio, Lakeway, and the surrounding communities:

• No trip fees
• No diagnostic fees
• Free estimates
• Available 7 days a week

Our technicians will accurately diagnose the cause of the leak and give you clear, honest options to get your system working properly again.

Call Air & Plumbing Today today or book online to schedule your appointment. We’re ready to help keep your home cool and dry.