Window Air Conditioner Leaking Water: How to Fix a Dripping Window AC Unit?

For every home with central heating and air, there are dozens with window air conditioning units. Part of the popularity is because window AC units are far cheaper than a central system. The best models can run you out of a room in minutes, but they are not without their faults. One of the most common concerns for homeowners with a window AC unit is dripping water, and it’s something you are likely to encounter eventually.

Whether you have significant water dripping inside your home or a steady trickle outside, correcting the problem can be a quick fix if you know where to start. That means you shouldn’t have to call in a professional if you follow our guide, which will show you how to take care of a window air conditioner leaking water.

Understanding Window Air Conditioning Systems

Window air conditioners are designed to fit into a wide variety of windows, including sliders that close from left to right and double-hung windows. Most people understand that cool air is blown into your home while exhaust heads outdoors, it’s a good idea to know a bit more about how a window AC unit works before attempting to fix a leaking water issue.

Window AC units are heavy but relatively simple once you peel back their shell. Different models can have slightly different styles, although they will all function in the same fashion. On the front, there are always a set of controls and a grill with a filter behind it.  Warm air passes in and through the filter before encountering the evaporator coil.

Beneath the cabinet cover, you’ll find a blower and fan on the inside of the unit on one side. On the other, there’s a compressor on the opposite side. While you’ll find some different bells & whistles depending on the style and type of window AC unit you choose, most will have a drain or drip pan, which deals with excess water caused by condensation.

Window AC Types

Keep in mind, there are several types of window AC units, including models with sling rings. They “sling” water onto the coil instead of draining it from the back of the system. Some of those models have drain plugs, whereas others do not, so get your manual handy if you have one or know the make and model before attempting to address any issue with your unit.

Fixing a Dripping Window AC Unit

One of the first things we want you to consider before breaking out your toolset or water hose is how long the unit has been leaking. Has it just been dripping over the past week, or does it happen on a seasonal basis?

That’s important to keep in mind, as some homeowners have been dealing with drips for years, while it may have become an overnight issue for others. Regardless of when the dripping started, it’s important to keep an eye on the situation and address it quickly.

You can wipe away water on hardwood or other bare flooring surfaces, but the damage may already be done if you have carpet and a continual drip you’ve dealt with seasonally for a few years. It’s also important to think about where your window air conditioner is placed and who installed it if you’re having a leaking problem.

Check the Drain Hole

The most common reason for a window air conditioner leaking water is because of a small hole on the back of the unit. It’s commonly referred to as a drain hole, and if it becomes clogged, water will have no place to go. That can cause it to drip water into your home quickly, depending on the weather outside and how long it’s in action on a daily basis.

Window AC Drain Hole

Look on the back or bottom of the unit to see if there is a noticeable clog. If you don’t see a hole, you may have a slinger fan or a system with a simple drain plug. If it’s plugged, remove the plug and allow any water inside to drain out.

With a sling-ring system that doesn’t have a drain hole, consult your user manual, but whatever you do, DO NOT drill a new hole in the bottom. It’s also important to know that some AC units require a little water inside to work efficiently, so again, read the manual when in doubt.

You will see countless threads online, and even a few videos that say drilling a hole in the bottom of your window AC unit will help with draining issues. Well, that can be true in certain conditions and climates, but it’s not a good idea. You could puncture your Freon line or damage another component, which will be an expensive mistake.

If you notice twigs, mud, or anything else blocking the drain hole, remove it, and you should see water begin to trickle out again. Even dirt and dust can clog up the drain port over time when there is no visible blockage. With drain pans, you simply need to remove the pan and empty if it’s full. It’s something you shouldn’t have to do on modern machines, however, unless you have the wrong type of system for your home or it’s malfunctioning.

Improper Installation 

Was your window AC unit installed by yourself and a few buddies over the weekend or by a professional? If you decided to take the DIY route, that could be the problem as the improper installation of a window AC unit is a big reason for leaks inside. If you’ve moved the unit from one room to another, installation is just as critical. You always need to check weather stripping, side retainers, and filler panels as well.

Window air conditioners with a drainage system should be tilted slightly backward more often than not. It’s an area where you’ll want to refer to the manufacturer’s instructions, but a level can tell you all you need to know. If your eyeballs or a level tells you the unit is tilted forward and your window air conditioner leaks water, the problem is apparent.

One reason your unit may have tilted from the time you installed it is brackets and rails. Vinyl window systems may have a safety lock in place, or you may find a couple of long screws securing the unit to the window sill. Ensure these are tight, and as they should be, and nothing needs to be replaced. The same goes for support brackets. Depending on the system, a quick adjustment to the bracket could be all you need to set your window AC unit straight again.

There’s no magic number for how far your unit needs to tile for perfect drainage, but Frigidaire recommends tilting the machine at least 2 – 4° downwards towards the outside of your home for several of their systems. For LG’s 7,500 BTU unit, they say a ½” will do the trick while GE recommends a 1/3 bubble using a level on a few of their systems. The point is, make sure you have enough of an angle for water to flow backward, not forward, and refer to your manual when in doubt.

The Filter

This one is hit or miss, but we’ve seen plenty of homeowners claim their window air conditioner stopped leaking water when they addressed this problem. Air filters or filters, in general, serve an essential purpose in any device. With window AC units, when your filter gets dirty, the system can bog down, and it can happen quickly depending on the air quality in your home.

Window Air Conditioner Filter

Air filters catch particles and dust as air is pulled into the system, and while it’s easy to forget to check them, it’s well worth your time. Cleaning an evaporator coil isn’t cheap or easy, so it pays to keep it your filter clean in order to prevent a variety of problems down the line. Rust and other things can build up in your system over time as well, so a good cleaning could solve your problem when all else fails.


Q: Why does my window air conditioner make a vibrating noise?

A: The vibration could be coming from the wall where the unit installed or because of improper installation.

Q: Why is my window air conditioner dripping outside when there’s no drain?

A: This is normal on many systems during weather where the humidity is high.

Q: My AC unit makes a pinging noise that’s annoying at night?

A: Generally, a pinging noise is water hitting the condenser, but it could also be water dripping into the pan if it’s dry. It depends on the model, but pings aren’t necessarily a sign of your system’s demise.

Written by

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree and EPA & R-410A Certifications.

2 thoughts on “Window Air Conditioner Leaking Water: How to Fix a Dripping Window AC Unit?”

  1. Why is my window ac unit dripping water from front of the unit just started it’s two years old. It’s tilted back the drain does not drain.


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