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Sizing the Right Air Dryer for your Air Compressor


Our experts have sold thousands or air dryers and water separators to remove water from your air compressor lines and we have put together a few questions to help you size the proper air dryer for your system. Note; we are not going to get too detailed but enough information to better help your air compressor system.


  1. What type of compressor do you have?
    1. Is it a piston/two stage air compressor?
      1. If it’s a piston, does it have an after cooler?
      2. Is it a rotary screw air compressor?
  2. What size is the compressor;
    1. Horsepower
    2. Capacity

Air Dryers are sized by CFM or capacity, so the information above will required to size the right dryer.

Sizing Example 1; I own a small manufacturing facility and I have a 25 hp two stage air compressor with no after cooler. This compressor puts out 95 CFM, 160 degree outlet air discharge temp, 125 psi. For this example, I would choose a 100 CFM high inlet temperature air dryer and I would install a pre dryer particulate filter and a post dryer coalescing filter ( coalescing filters best at the coldest spot, which is after the dryer)

*Air Compressors without after coolers have a high discharge temperature, any compressor with a outlet temperature of over 100 degrees F should have an after cooler/exchanger installed prior to the air dryer or install an all in one high inlet temperature air dryer.

Here is a quick sizing chart to help you size the right dryer;

HP Capacity 
High Inlet Temp (HTD) Dryer
*Refrigerated Air Dryer (+39)
*Refrigerated Air Dryer (-40)
5 17 20 CFM HTD 20 CFM 20 CFM
7.5 25 25-30 CFM HTD 35 CFM 35 CFM
10 35 35-50 CFM HTD 50 CFM 50 CFM
15 55 75 CFM HTD 75 CFM 75 CFM
20 80 100 CFM HTD 100 CFM 100 CFM
25 105 125 CFM HTD 125 CFM 125 CFM
30 125 125-150 CFM HTD 150 CFM 150 CFM
40 170 200 CFM HTD 200 CFM 200 CFM
50 220 250 CFM HTD 250 CFM 250 CFM
75 350 350 CFM HTD 400 CFM 400 CFM
100 450 C.F. 500 CFM 500 CFM

*Standard Refrigerated & Desiccant Air Dryers require an inlet temperature of 100 degrees F or less
** Also take your inlet air pressure into consideration when sizing. Understand the pressure limitations to your air dryer.

The air dryer suppresses the dew-point, which removes the bulk of the moisture in the lines. You should also know that installing the following components will increase the success of your air dryer, here are a few suggestions;

  • Install a water separator before the dryer (many rotary screw compressors have this as a standard line item).
  • Install a pre filter before the dryer (many dryers extend their warranty with a pre-filter purchased with the dryer).
  • Install a post filter after the dryer (this helps remove any oil and a coalescing filters best at the coldest point).
  • Install a 3 valve bypass around the filters and dryer (this helps with servicing and related maintenance).

Here is a great infographic that shows a typical air compressor system.

Typical Air Compressor System

Applications vary and so does the air quality for your process. Here is a great table that shows what you may need to achieve a certain classification of air quality.

Air Quality Table

Feel free to contact any of our experts for related sizing, pricing and/or free consultation.

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