Why Is My AC Drain Pan Full Of Water?

Nathan Rizzuti Profile image

Written by:

Updated December 23, 2022

Even the best air conditioners need maintenance to keep them effective and running for a long time. Every homeowner should educate themselves on the main components of their air conditioner, which allows them to check for signs of damage. One common area of concern is the unit’s drainage system. To help you understand what this entails, below, we’ll answer the question: Why is there water in my air conditioner drain pan?


  • Drain pans protect units from water damage by collecting any excess water that falls from the evaporator coils. If the pan overflows, it can cause severe damage to the AC unit.
  • The leading cause of overfull drain pans is debris and dirt from the condensation caught in the unit’s drain line.
  • Low refrigerant levels cause the evaporator to frost over, which rapidly fills and sometimes overflows the drain pan.

Insider Tip

To avoid drain pipe blockage, check for dirty air filters as a part of regular maintenance.

For those dealing with air conditioning issues, we have a helpful article explaining when a home warranty will replace an air conditioner.

Why Water Is in Your Air Conditioner Drain Pan

Drip pans are found in all types of air conditioning units and are located underneath the evaporator coils. The purpose of a drip pan is to catch any excess water that falls from the coils so that it doesn’t leak into the system. The pan is connected to a drain line that disposes of any water from the evaporator coils. However, when the air conditioner drip pan overflows, it can lead to water damage throughout the entire unit. Keep in mind that investing in a unit that’s rust-resistant like the AC unit we discuss in our Portacool PACCYC06 review can avoid that water damage and eventual rust too.

A full drain pan is not something to take lightly. More often than not, excess water signifies something has gone wrong. This can also explain why your air conditioner sounds like running water. The best thing to do about full drip pans is to contact an HVAC professional to examine and fix your unit to avoid further damage.

Clogged Drain Pipe

The most common culprit of an overflowing AC drip pan is a clog in the condensate drain. Such clogs often occur because of a dirty air filter. This causes dirty air to flow over the evaporator, which condenses the moisture, dirt, and debris in the air, where it collects on the coils. The water, dirt, and debris eventually drip into the pan. Then, it gets caught in the AC drain condensate line. If the dirt is excessive and stays in the line for too long, it grows mold and algae, creating a greater blockage.


If a drip pan has standing water in it for too long, it can rust and develop holes, at which point you will need to replace the pan.

Frozen Evaporator Coils

When the unit’s refrigerant levels get low, the coils can freeze and become caked in frost. The frost melts from the frozen coils and fills up the drain pan quicker than usual. Call an HVAC professional to address this issue if you notice frosty coils.

STAT: Forty percent of all cases of overflowing drain pans stem from clogged drain pipes. (source)

Why Is There Water in My Air Conditioner Drain Pan FAQs

How do I stop my AC drain from clogging?

Purchasing high-quality air filters are a great way to reduce the amount of debris within the airflow. If you have a reusable filter, perform routine cleaning with soap and water.

How do you unclog the air conditioner drain line?

Unclogging the drain pipe requires dismantling the drainage equipment, inspecting the line for damages, and cleaning it with a wire brush and bleach compound.

How much water should there be in the AC drip pan?

If the drain line is free of debris, the unit should have a small amount of water in the drip pan when it is on.
Nathan Rizzuti Profile image