Water in Your Air Compressor? Here’s What to Do About It

Water in your air compressor can cause a whole range of problems if it is allowed to build up. When the water becomes a problem depends largely on what you’re using the compressor for. Some applications require extremely dry air while others do not. Either way, it’s essential to know how to deal with water in your air compressor. 

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Why Is There Water in My Air Compressor?

It’s impossible to prevent water from getting into your air compressor. This is because all air has moisture in it. Compressing air necessarily causes that water to turn from its vapor form into liquid as it condenses. When it builds up enough, it can make its way into the compressed air stream. 

How fast water builds up in your compressor depends on the temperature and humidity in your area. Warmer air can hold more moisture, so the summer months can cause quick build ups of water in your compressor — especially if you live somewhere with high humidity. 

However, no matter the season or temperature, there’s always moisture in the air. This is why it’s important to remove moisture from the compressor all year round. 

These machines compress air to about 12 times normal pressure, and compressed air can’t hold as much moisture. So as the air is compressed, condensate forms inside the system, usually in the receiver tank and other components. 

When moisture is allowed to get in the compressed air stream, it can cause a wide range of problems. These include application issues and even damage to the compressor. 

Can Moisture Cause Damage to the Air Compressor?

Water in your air compressor can cause damage to the system in several different ways. These include corrosion, instrument malfunction, water hammer, and ice formation in cold temperatures. These can all be avoided with proper maintenance and prevention. 


The biggest concern is corrosion. Moisture, air, and metal are all players in corrosion, and all three are constantly interacting inside the air compressor. So when moisture is allowed to remain in the system, it can cause corrosion, which is detrimental to the life of the compressor. 

Believe it or not, too much corrosion can even cause an air compressor to explode. As corrosion eats away at the inner metal of the air tank, it weakens the integrity of the tank. And if allowed to continue, the pressure inside the tank can become too much, causing the compressor to rupture. 


Water can also cause instrument malfunction by blocking control lines. It can also cause water hammer, which is identified by a knocking sound in the compressor’s pipes. This can damage the compressor and should be avoided through the tips outlined below. 


Lastly, water in the compressor can freeze in cold temperatures. And as we all know, water expands when it freezes. This can crack pipes and damage other compressor components. Frozen water in the compressor can also block filters and intake drain valves, affecting system performance. 

But the negative effects don’t just pertain to the system itself. Water can also affect the performance of the system when it gets into the compressed air stream.   

The Effects of Water in Compressed Air Stream

Certain compressor applications can suffer from water in the air stream. Two major examples are spray painting and sandblasting. Moisture in the air stream when spray painting can negatively affect the texture and finish. When sandblasting, moisture can waste abrasive and decrease efficiency. 

A high humidity percentage or liquid water in the air stream can also affect lubrication and result in corrosion of air tools. If rust particles get into the air stream, they can damage equipment and generally affect production and performance. 

How to Drain Water From an Air Compressor

It’s important to drain your air compressor regularly. Luckily, this is easy to do with the air compressor drain valve located on the underside of the air receiver tank. Make sure you wear proper protective gear any time you’re working on a compressor. Here’s how to drain the air receiver tank. 

1. Turn Off the Compressor

The compressor should be off in order to drain the tank. But there does need to be air in the tank still. Around 30 psi should be enough to facilitate drainage.

2. Open the Valve

Locate and open the valve. If the compressor hasn’t been drained in a while, you’ll probably get a rush of water coming out. If it has, you’ll get water and a rush of air coming out. 

3. Tilt the Compressor

Most drain valves are located off-center for clearance. This means that in order to get all the water out, you may need to tilt the compressor toward the valve so the water will pool there and come out. 

4. Repeat as Necessary

If the air in the tank releases fully before the water stops coming out, you may need to close the valve and turn on the compressor to put more air in the tank and then repeat steps 1 through 3 above. If you drain the tank regularly, you shouldn’t have to repeat those steps. 

While draining is important, there are other ways to keep moisture from affecting your air compressor. Depending on what you use your compressor for, some of the tools recommended below may be essential.

How to Keep Moisture Out of Your Air Compressor

There are many ways to keep moisture out of your air compressor. Usually, some combination of them works best. 

Electronic Auto Drain Valve

Auto drain valves are great if you have trouble remembering to drain your compressor or you simply want a more convenient way to do it. These operate on a timer, opening the drain valve when it’s time so you don’t have to. 

They’re inexpensive and easy to use. All you have to do is install one, plug it into a wall outlet, set the time, and forget it.

Water Separator Filter

Installing an in-line water separator filter can also help keep moisture out of your compressed air. These are especially helpful for projects like spray painting with small compressors that otherwise allow too much moisture in the air stream. These filters can remove 40% to 60% of the moisture in the compressed air. 

Refrigerated Air Dryers

Refrigerated air dryers are another option for managing moisture in your air compressor. Refrigerated air dryers take advantage of the fact that cold air is able to hold less moisture than warm air. They work similar to an air conditioner or refrigerator, extracting moisture from the air and releasing it to the drain. 

These are ideal for protecting the air compressor and air tools as well as ensuring proper operation. They’re especially useful for those who need low-moisture air consistently and repeatedly.

Desiccant Air Dryers

Another option for keeping moisture out of your air compressor is a desiccant air dryer. These filters work with the use of activated alumina, silica gel, or molecular sieve. The small beads in the air dryer help remove moisture as the incoming air passes through them. 

There are generally two processes that occur in desiccant air dryers: moisture collection by the desiccant beads and a heating cycle that removes the moisture from the beads so they can continue to remove moisture from incoming air.

Homemade Water Separator Air Compressor

If you need to keep moisture out of your air compressor and you’re looking for a fun project, you can always build yourself a water separator for your air compressor. There are many different ways to do this, each of which depends on your specific needs, budget, space, and how dry you need your compressed air to be. 

Here are just two examples of very different DIY water separators for air compressors. 

Do Air Compressors Need to be Drained After Every Use?

How often you need to drain your air compressor depends on how much you use it and what you use it for. The intake of air into your compressor is directly related to the intake of moisture. The moisture volume will vary depending on the ambient temperature and humidity. 

In short, the more you use your compressor, the more moisture will build up inside it. And the more moisture, the more often you’ll need to drain it. So while you may not need to drain it after every single use, it’s best to drain it at least once a day. 

How Often Do Air Compressors Need to be Drained?

As mentioned above, an air compressor that sees daily use should be drained daily. At minimum, a compressor should be drained once a week. If you don’t think you’ll be using your compressor for a while, drain it once you’re done with it to prevent corrosion. 


There’s no getting around moisture in your air compressor. But there are many different ways that you can limit the amount of moisture that ends up in the air stream. By using the right tools, such as desiccated air dryers, water separator filters, and refrigerated air dryers, you can control the moisture in your air compressor enough to get any project done, no matter how moisture-sensitive. 

Even if you’re not doing anything that moisture can necessarily affect, there’s still the compressor itself to think about. Draining the receiver tank on a regular basis is important for maintaining the health of the compressor. And for your convenience, an electronic auto drain valve can do this for you at timed intervals.

Water In Your Air Compressor FAQ’s

What are the common methods for removing water from an air compressor?

There are two primary methods for removing water from an air compressor: refrigerated air dryers and desiccant air dryers. Refrigerated air dryers work by cooling the compressed air to a temperature below its dew point, which causes water vapor to condense into liquid form. Desiccant air dryers, on the other hand, use a desiccant material to absorb moisture from the compressed air supply.

What is the impact of air temperature on water in an air compressor system?

Air temperature plays a crucial role in the formation of water in an air compressor system. As the air temperature increases, the amount of water vapor it can hold also increases, which can lead to higher levels of excess moisture in the compressed air supply. This can be especially problematic in humid environments or during the summer months when air temperatures are higher.

What is the pressure dew point, and why is it important in air compressor systems?

The pressure dew point is the temperature at which water vapor begins to condense at a specific pressure. It is an essential metric for determining the amount of moisture in the compressed air supply and ensuring that the compressed air quality meets specific standards. Maintaining a pressure dew point that is below the ambient air temperature is critical for preventing excess moisture in the compressed air supply.

What are the consequences of poor quality compressed air caused by water in the system?

Poor quality compressed air caused by water in the system can lead to a range of issues. For example, excess moisture in the compressed air can cause corrosion of compressed air lines, damage to pneumatic tools, and decreased overall system efficiency. In addition, water in the compressed air supply can affect downstream equipment and processes, leading to product defects or other quality issues.

What are the air drying components of an air compressor system?

The air drying components of an air compressor system include refrigerated and desiccant air dryers, as well as filters, drain valves, and piping system air drying. Refrigerated air dryers work by cooling the compressed air to remove water vapor, while desiccant air dryers use a desiccant material to absorb moisture. Filters remove particulates and other impurities from the compressed air supply, while drain valves allow for the removal of excess water.

What are some best practices for managing water in industrial air compressors?

Best practices for managing water in industrial air compressors include regularly checking and maintaining air drying components, monitoring pressure dew points, and ensuring proper airflow through the system. It’s also important to use high-quality air filters and to install a moisture removal system to minimize water buildup and maintain optimal compressed air quality. In addition, proper system design and installation can help to prevent water from entering the system in the first place.


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