How Much Water is in Compressed Air and How Much Does Each Dryer Type Remove?
A compressed air system pulls in far more water than most operators expect, and how much moisture stays in the air depends entirely on how it’s dried. Untreated air can carry many gallons of water per week into a plant. A refrigerated dryer cuts that to a fraction, and a desiccant dryer removes nearly all of it. Tavoron’s moisture load calculator estimates the water in a system and how much each drying method removes, per week and per year.
Why is There Water in Compressed Air?
When ambient air is compressed, several things happen that cause water to enter the compressed air system. Air compressors draw in ambient air, which naturally contains water vapor. During the compression process, the temperature of the air increases. The hot air easily holds the water vapor, but as the compressed air cools, its volume shrinks, while its moisture content remains the same. When this occurs, the excess water vapor condenses into liquid form and enters the compressed air system.
How Much Water is in Compressed Air?
Exactly how much water is in the compressed air depends on several factors, including ambient air temperature, relative humidity, and air volume, but for reference, a typical air compressor operating in average summer conditions can easily produce 15 to 20 gallons of water per day.
Here’s why temperature, humidity, and volume matter:
- Ambient air temperature: Warm air holds more water vapor than cold air. As ambient air temperatures rise, so does the moisture capacity of the air. This means the air drawn into a compressor on a hot summer day contains more water than it will on a winter day.
- Relative humidity: Humid air contains high levels of moisture, so higher humidity levels in the intake air result in more water vapor being drawn into the system.
- Air volume: Every cubic foot of ambient air contains a specific weight of water based on the temperature and humidity of the air, so if you double the volume of air you compress, you double the amount of liquid water generated. This means if you are operating tools that demand a high, continuous volume of air, your compressor will run longer and draw in more air – and more air volume equals a higher water payload.
How to Remove Water from Compressed Air
To avoid issues with rust, corrosion, and product degradation caused by moisture in the compressed air system, water must be removed, and this requires the use of an air dryer.
What are the Compressed Air Dryer Types?
There are several types of compressed air dryers, including refrigerated, desiccant, and deliquescent dryers.
Refrigerated dryers:
Refrigerated dryers chill compressed air to dew points around 35°F and remove between 85% to 90% of the water from compressed air.
Desiccant dryers:
Desiccant dryers use a desiccant material to absorb water vapor from the air stream and can remove about 99.9% of water from the air.
Deliquescent dryers:
These dryers, also called chemical dryers, use deliquescent chemicals (such as sodium) to absorb between 75% and 80% of the water from compressed air.
Aftercoolers:
Technically a compressed air dryer, aftercoolers cool the hot compressed air as it is discharged from the compressor. They help prevent liquid from entering the compressed air system, but are typically not a stand-alone drying method.
Each of these air compressor dryer types offers a different water removal efficiency at a different dew point. The table below offers a comparison:
| Dryer Technology | Dew Point | Water Removal Efficiency |
|---|---|---|
| No Treatment | Equal to the ambient temperature. | 0% (Liquid water and vapor remain in the system) |
| Aftercooler | Depends on ambient temp and cooler approach temp; typically 85°F to 100°F. | 60% to 70% of total liquid water. |
| Deliquescent | 20°F to 50°F | 75% to 80% of total liquid water. |
| Refrigerated | 35°F to 50°F | 85% to 90% of total liquid water. |
| Desiccant (twin-tower) | - 40°F to -100°F | 99.9%+ (removes nearly all water vapor). |
What is Compressed Air Dew Point?
The table includes the dew point temperature for each dryer type. Compressed air dew point is the temperature at which the water vapor in the compressed air transforms into liquid condensation. The lower the dew point temperature, the dryer the air, and, conversely, the higher the dew point temperature, the more moisture the compressed air will contain.
How to Estimate Your System’s Moisture Load
Because there are so many variables, it can be difficult to determine your system’s moisture load – and the best dryer for your application. Tavoron offers a Moisture Load Calculator that estimates the water in a compressed air system and how much each drying method removes, per week and per year.
How to Choose the Right Compressed Air Dryer Type for The Application
There are a few considerations when choosing a compressed air dryer type for your system:
- Temperature and humidity: The environment where your compressed air system is located is an important factor because a hot, humid environment will produce more water than a less humid one.
- Dew point: Compressed air dew point is another major factor. As mentioned earlier, the lower the dew point temperature, the dryer the air.
- Application: An air dryer should be selected based on its ability to meet the specifications of the application.
Based on these factors, the following dryer types are recommended for the following applications:
| Dryer Technology | Dew Point | Best For |
|---|---|---|
| Deliquescent | 20°F to 50°F | Outdoor, remote, or hazardous environments (oil/gas, sandblasting) where electricity isn't available. |
| Refrigerated | 35°F to 50°F | General manufacturing, machine shops, and automotive applications where air lines aren't exposed to freezing temperatures and product degradation is not a concern. |
| Desiccant (twin-tower) | - 40°F to -100°F | Critical applications, electronics manufacturing, pharmaceuticals, food processing, and outdoor air lines exposed to sub-freezing environments. |
FAQ
How much water does a compressed air system produce?
The exact amount of water in compressed air depends heavily on the temperature and humidity in the ambient air. But, a typical compressor running in average summer conditions can produce 15 to 20 gallons of water per day.
Which compressed air dryer type removes the most water?
Desiccant dryers remove the most water: 99.9% of the water can be removed from the air stream.
What dew point do I need for my application?
The required dew point really depends on the application. Sensitive applications, such as pharmaceutical processing, electronics production, and other industries that are regulated for compressed air quality, will need lower dew points because the lower the dew point temperature, the less moisture in the compressed air.
Do I need a refrigerated vs. desiccant dryer?
That depends on your application. Refrigerated dryers are often used in general and automotive manufacturing where moisture needs to be removed to protect equipment, but compressed air quality is not regulated and some level of moisture will not degrade product quality.
Desiccant dryers, which remove 99.9% of the water from the air stream, should be used in critical applications, such as food processing, medical device manufacturing, and electronics manufacturing.
Talk to Tavoron about the Right Dryer for Your Application
Don’t let water in compressed air damage your tools, product quality, or reputation. Estimate your moisture load using Tavoron’s moisture load calculator and then get in touch with a Tavoron expert for a compressed air audit, assistance with finding the right air compressor dryer type, or help sizing a dryer for your application.
