Radon is a serious health risk, but with the right mitigation system, you can protect your home and family. One of the most critical steps in the process is selecting the correct radon pipe size. This blog post breaks down the key factors and steps involved, based on our video Choosing the Right Pipe Size: Avoid These Common Mistakes!
Step 1: Determine How Much Air You Need To Move
Before you can choose a pipe size, you need to know how much air the system needs to move to hit the target pressure field extension. The goal is to create negative pressure in the weakest test hole. The video demonstrates a method for doing this by using a shop vac and a pitot tube to create suction [00:25].
Step 2: Measure Velocity Pressure In The Pitot Tube
Once you’ve achieved the target pressure, the next step is to measure the velocity pressure. This measurement can be found on the micro manometer*. In the video’s example, the velocity pressure was 10 pascals [01:10].
Step 3: Use a Chart to Find CFM
With the velocity pressure reading in hand, use the Velocity Pressure (Pa) Vs. Cubic Feet Per Minute Chart, to find the corresponding CFM. A velocity pressure of 10 pascals in a 2-inch pitot tube corresponds to moving around 16 to 17 CFM [01:18].
General Rules for Pipe Sizing
The video provides some general guidelines for pipe sizing based on the CFM you’ve calculated:
- 2-inch pipe: Suitable for moving less than 35 CFM. However, if the system has many fittings, a 3-inch pipe might be a better choice to account for friction loss [01:42].
- 3-inch pipe: Recommended for moving between 40 and 60 CFM [01:53].
- 4-inch pipe: Needed to move 60-70 CFM or more. This will allow for greater airflow without the need for a larger fan [02:02].
By following these steps and guidelines, you can ensure your radon mitigation system is sized correctly for maximum effectiveness. For more detailed information on measuring pressure field extension, check out our course, Engineering and Radon: Designing an Effective Mitigation System.
*American Radon Mitigation earns a commission through some of the links in this blog post. Thank you for your support.
