AIR FLOW PRESSURE DROP IN TYPICAL RADON PIPING

The radon industry typically uses plastic piping from 2" to 6" in diameter in the installation of active soil depressurization systems (ASD). It is also typical to use 2" by 3" or 3" by 4" aluminum downspout for exterior piping. In a previous paper, (ref I), the exhaust airflow in 87 NJ ASD mitigation systems was measured from a low of 11 ch to a high of 167 ch with a median level Of 70 cfin. Fifty-six percent of these systems had air flows between 40 and 90 cfin. These typical air flows can have a large pipe pressure drop because of the system design that will reduce the systems final effectiveness. Most radon mitigators have little idea how much impact changing the pipe size has on their final system performance or how to calculate the pipe pressure drop. This paper discusses the development of a pipe pressure drop calculation for standard mitigation piping and fittings. The formulas for calculating the pressure drop were obtained from the ASHRAE Handbook of Fundamentals (ref 2). Correction factors for these formulas and testing of fittings and piping not included in the Fundamentals were obtained by carefully testing the pressure drops in the range of air flow and pipe sizes previously mentioned. The pressure drop in pvc piping was found to be from 9% to 23% less than the ASHRAE calculations. The pressure drop in pvc fittings was found to be from 53% less to 109% greater than the ASHRAE calculations. Using the corrected values attained from the study, a spreadsheet program was developed to allow easy calculations of pressure drop in a radon system. AARST will be offering copies of this spreadsheet program to its members. Two typical radon mitigation system layouts are used to demonstrate the expected pressure loss that would occur with typical airflows and different piping sizes. Some general system installation recommendations are made in the final analysis.