Informational Guide

How To Drain Air Compressor

In this guide, we teach you how to drain air compressor to keep it in working order.

As a mechanic, you are constantly using your air compressor to make your jobs easier, but you must also think about the ways to keep it running at optimal levels. One maintenance task worth learning is how to drain an air compressor.  

In this article, we will cover how to drain air compressor tank and how to install an air compressor automatic drain.  

Why should you learn how to drain an air compressor of water? After all, it’s just easier to ignore the compressor until something goes wrong. As part of regular maintenance, you must know how to drain water out of an air compressor. Otherwise, you could run into these troubles. 

  • Decrease In Air Volume  
    As water builds up in the tank, there is less volume available for the air. You will wait longer for the tank to fill because of this water.  
  • Rusting  
    When oxygen and water mix, rust occurs. If the tank begins rusting, you will have no option but to replace it.  
  • Risk Of Bursting  
    The air compressor is only designed to hold a certain amount of pressure. When rust occurs, the walls become thinner, and the tank will not be able to endure the pressure anymore, causing it to burst.  
  • Disturbance With Air Tools  
    Air tools don’t work well with water. For example, if you get water into your paint sprayer, there will be uneven spray coming out of the tip, causing a poor-quality paint job.  
draining an air compressor

How Does Water Get In Air Compressors? 

Before you think about how to replace an air compressor drain valve, consider how water might have gotten inside in the first place. When the air compressor is on, it sucks air inside the tank to compress it. In this air, there’s always a little bit of moisture contained from the water vapor and humidity.

This vapor condenses into droplets that can build up and turn into the free-flowing liquid inside the compressor. To correct the problem, you must know how to drain water from an air compressor. 

Where Is The Air Compressor Drain Valve? 

Before you figure out how to drain a Porter Cable air compressor, you must first find the valve for draining. So which valve is the drain valve?

It's the one found at the bottom of the compressor tank.

The reason for it to be at the bottom is to ensure all of the water inside of the tank drains out.  

Whether you are learning how to drain a Husky air compressor or how to drain water from a Craftsman air compressor, the valve should always be in the same location.

This universal design ensures you get the tank drained quickly and efficiently.  

air compressor drain valve

How To Drain An Air Compressor (Easy DIY Water Removal Guide) 

Manual Draining 

It doesn’t matter if you want to know how to drain a Campbell Hausfeld air compressor or how to drain a Bostitch air compressor. These are the steps you will follow if you need to manually drain the tank of water or built-up moisture. 

  1. 1
    Turn off the compressor. Not only should you ensure it is off, but you should also unplug it. This step is designed for your safety. 
  2. 2
    Reduce any pressure in the tank until it reads below 10 PSI (pound per square inch). You do this by pulling on the ring found on the safety valve. You should always wear safety goggles while performing this step.  
  3. 3
    Open the drain valve. It will be found on the bottom of the compressor tank. Some models use reversed threads, so you will need to figure out how to remove them. When the drain valve is opened, the moisture should escape with ease.  

Automatic Draining 

Whether you want to know how to drain a Craftsman air compressor or how to drain a Dewalt air compressor, you might have a model that is compatible with automatic draining. With this type, the water that has accumulated will be expelled with the compressed air. Thanks to this design, you won’t need to drain the tank manually anymore.  

Plus, this type of tank ensures that moisture doesn’t build up in the tank, so there’s less chance of corrosion and rust. If your compressor doesn’t have an automatic drain, you can install one for more convenience.  

There are also some models that allow for timing the job. You can set how long and how frequently the draining occurs. To install the new drain, simply unscrew the old one and put the automatic one in its place. Don’t forget to plug it in. If it has a timer, you will also want to adjust the settings before using it.  

How Often Should You Drain An Air Compressor?

To determine how often to drain an air compressor, you must look at the size. The commercial or larger air compressors should be drained daily, or every time they are used. However, the answer to how often to drain an air compressor tank is different with smaller models. These could go longer, but to be on the safe side, you might prefer to do it every time.  

how often to drain air compressor

People Also Ask (FAQs)

How long does it take to drain an air compressor? 

Releasing the pressure from the tank will probably take the longest. However, you only need a few minutes to get all of the moisture out of your compressor, so there’s no excuse to avoid performing the job.  

How much water will my compressor create? 

For every ten horsepower of compressor capacity under a full load, you get about 2,500 cubic feet of compressed air each hour. At this rate, 0.2 gallons of water would compress every hour the compressor is in use.  

How do you stop water from building up in an air compressor? 

While some people leave the drain open slightly, there are two better solutions. First, use a high-quality air filter and separator to keep water out. Additionally, you use a refrigerated air dryer to ensure less moisture.  

Should there be some air pressure in the tank to help drain it? 

If you read any of the owner manuals, the instructions will tell you to reduce the pressure to 10 PSI before draining the water out of the tank. While unwise, some people choose to do it differently.  


Now that you know how to drain water from an air compressor tank, it’s time for you to maintain your equipment for a longer life. This simple step keeps your compressor running the way it should for increased durability.