Why Your Air Conditioner Is Leaking Water and How to Prevent It

If you've ever walked past your air conditioner and noticed a puddle forming underneath, it can be confusing and worrying. After all, air conditioners are supposed to cool your home, not let it in. While some condensation is normal, visible leaks or drips usually indicate something is wrong. Understanding the cause of the leak is the first step to preventing water damage and keeping your system running smoothly.

Why is there water?

Air conditioners work by drawing warm, humid air from your home, cooling it, and pushing it out. During this process, moisture in the air condenses on the evaporator coil (just like water droplets forming on cold glass). This moisture then drips into a collection pan and exits the home through a condensation drain pipe. Under normal conditions, this system operates quietly and efficiently.

But when this process is interrupted, even in a single small spot, water can start leaking where it shouldn't.

Common causes of air conditioner water leaks

Clogged condensation drain

The most common cause of air conditioner water leaks is a clogged drain pipe. Over time, dirt, dust, mold, and algae can build up inside the drain pipe, preventing water from draining properly. When the pipe becomes clogged, water backs up and leaks out of the drain pan, often causing stains on the ceiling, damage to the walls, or puddles near the indoor unit.

Cracked or rusted drain pan

Older systems often have a corroded or cracked condensation drain pan. If the pan fails to retain water or direct it to the drain pipe, it will leak into the surrounding area. This is especially common in systems that are more than 10-15 years old.

Dirty Air Filters

Believe it or not, a dirty air filter can contribute to water leaks. When filters are clogged, airflow over the evaporator coil is reduced, which can cause it to freeze. When it eventually melts, all that water can clog the drain system and leak out.

Low Refrigerant Levels

A low refrigerant level can also cause coils to freeze, and just like dirty filters, melting ice can cause excessive water leaks. A low refrigerant level is a more serious problem, as it often indicates a leak in the system that requires professional repair.

Improper Installation or Slope

If the air conditioner or drain pan is not level, water may not flow properly into the drain line. Instead, it may overflow over the edges and leak into your home. This is a common problem with new installations or DIY installations.

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