Why is my air conditioner leaking water inside my home?

So here’s the bottom line: Yes, your air conditioner produces moisture during normal operation (more on that later).

BUT  you should never see water leaking from the unit—if everything is working properly, that moisture drains safely away outside via “condensate drain lines”.

So, you’re right to be concerned that water is leaking from your air conditioner and into your home. But don’t worry—in this article we’ll explain what’s going on and how to fix the problem.

First, do this: Go to your thermostat and switch it OFF so your AC turns off and water stops leaking into your home.

Now, usually 4 problems cause your air conditioner to leak water:

  1. Clogged condensate drain line
  2. Rusted drain pan
  3. Broken condensate pump
  4. Frozen evaporator coil

Need help right away? Give us a call or contact us online, and we’ll quickly send over one of our trusted technicians to stop your air conditioner from leaking water.

We’ll go into more detail about each of these 4 common AC problems. But before we dive in, let’s briefly look at why water forms in your air conditioner.

Why your air conditioner produces moisture in the first place

Your air conditioner has an important component called the evaporator coil. The evaporator coil is filled with very cold refrigerant that basically sucks all the heat right out of your home’s air.

So, after warm air passes over this A-shaped contraption, you get cool, conditioned air. That cool air is what comes out of your vents and lowers the temperature of your house.

An evaporator coil

But when warm air hits the cold refrigerant coil, it forms condensation (moisture). Think of a cold glass of water on a hot summer’s day—those little beads of water that form on the glass are condensation.

Now, over time, those tiny beads of condensation on the evaporator coil collect and produce a considerable amount of moisture.

So where does this moisture go in your air conditioner?

Well, normally these drops of moisture drip into a drain pan, and exit your house via a condensate drain line (the white PVC pipe you may have noticed outside your home, pictured below).

But if there’s a problem somewhere in the condensate draining process, then all that water may start leaking into your home.

Let’s take a look at those 4 problems we mentioned in the beginning…

Problem #1: Clogged condensate line

A clogged condensate line is the most common cause of water leaking into your home from your AC.

Overtime, this drain line gets clogged up with dirt and debris which prevents the water from exiting your home. Since this water has no where else to go, it flows back into your drain pan. Once enough water builds up in your drain pan it can overflow.

Indoor condensate drain line

Solution: Have a professional use a special vacuum to suck out all the blockage material.

Problem #2: Rusted drain pan

If your drain pan is rusted, it will develop holes and spill water around your indoor air conditioning unit.

The drain pan is located below the air handler (indoor part of your air conditioner), which is usually in your attic or a closet.

Solution: If you know the dimensions of the drain pan, you can go to a home improvement store and pick up a replacement, or you can call a professional for help.

Problem #3: Broken condensate pump

Are your air conditioner and furnace in the basement? If so, you have a condensate pump. This pump moves condensate water upwards so that it can be dumped outside your home.

But if the condensate pump breaks, water won’t be pumped outside, leaving you with a pool of water inside.

Solution: You’ll need an air conditioning professional to repair or replace the pump.

Problem #4: Frozen evaporator coil

This may seem strange but on especially on hot days, your air conditioner can actually freeze. More specifically, the evaporator coil can freeze.

Like we mentioned earlier, the evaporator coil is that A-shaped device that’s responsible for cooling your home’s air. But 2 issues can cause it to freeze up:

  • Low airflow
  • Low refrigerant

Once the evaporator coil freezes, your AC can’t cool your home. Plus, when the thick coat of ice eventually melts, it can overflow from the drain pan and flood the area surrounding your indoor air handler.

Let’s look at how to troubleshoot those 2 issues we mentioned…

Low airflow

If your evaporator coil doesn’t have enough warm air from inside your home blowing over it, the refrigerant coils get way too cold. And when it gets too cold, all the condensation from the air will freeze on the coils and build a hunk of ice over the evaporator coil. Once the ice melts, you’ll have water leaking out of your air conditioner.

The following issues restrict air from reaching the evaporator coil:

  • Dirty air filters
  • Closed vents and blocked registers
  • Blocked or leaky ducts


  • Change your air filters when they’re dirty
  • Leave all the vents and registers in your home open and unblocked
  • Contact a professional to seal any leaks in your duct work

Low refrigerant

Your evaporator coils use refrigerant to remove heat from the warm air in your home. If your AC system’s refrigerant levels drop too low, though, your evaporator coils will get too cold and condensation will start freezing on the coils. Once the ice melts, water can overflow from the drain pan.

Now the only way to have low refrigerant is if you have a leak in the refrigerant lines somewhere in your system. (Refrigerant isn’t like gas in a car—your AC shouldn’t run out of refrigerant unless there’s a leak).

You’ll know you have a refrigerant leak if…

  • You hear a hissing/bubbling noise
  • The air conditioner isn’t cooling your home well
  • You feel warm air coming from your vents

SolutionContact a professional to repair the refrigerant leak so your evaporator coil doesn’t freeze.

Need AC help from a Kansas City professional?

Contact us today to schedule an appointment with one of our techs so they can fix whatever is causing your air conditioner to leak.