Plumbing Engineer June 2021/37
IAPMO 2021 UPC, Appendix N One of the most important Legionella standards for building water system design operation and maintenance is the IAPMO 2021 Uniform Plumbing Code Appendix N (Figure 1). It simply and clearly names various tempera- ture ranges from cold to disinfecting hot and identifies the temperatures in each range. For each temperature range, it presents both the scald and Legionella -related risks. Many believe that addressing the Legionella issue results in increased scalding risk. Appendix N shows this is not the case. Effective Legionella control can be imple- mented while effectively controlling scalding risk. The Legionella control temperatures in Appendix N agree with the temperatures listed in ASHRAE Guideline 12 2020 and most other Legionella guidance documents. This IAPMO UPC Appendix was developed by a diverse committee of plumbing system design experts, mas- ter plumbers, Legionella control experts and academic researchers. An important caveat in this appendix is Note 2, which states these temperatures were determined in a lab setting in the absence of a realistic microbial community. All pub- lished research on Legionella control temperatures uses these same criteria to limit the number of uncontrolled variables. Also, this note states that Legionella can survive for longer periods of time at temperatures higher and lower than the growth ranges indicated. One item missing from Note 2 that is well understood is these temperatures were also determined in the absence of any disinfectant residual. Importantly, this standard addresses a pervasive miscon- ception that Legionella control means more costs in energy and water and chemicals. This is not the case. Good plumb- ing system design will save water, energy and construction costs while dramatically reducing Legionella risk as well as operational and maintenance costs. Understanding the role of temperature in plumbing system design, operation and maintenance is critical to effective, as well as cost- effective, control of Legionella . The recommended temperature range listed in this UPC document for the best Legionella control with low scald risk is the tempered hot range of 120 F to 130 F (49 C to 54 C). It is typically found in sinks and showers at good hotels. This tempered hot range was the basis of the Department of Veterans Affairs VHA Directive 2009-009 titled, "Domestic Hot Water Temperature Limits for Legionella Prevention and Scald Control." This 2009 VA Directive (https://bit.ly/3nw92Fo) was successfully implemented at many VA hospitals with no Legionella or scalding issues. These temperature ranges were removed from VA guid-
Figure 1. Comparing Scald and Legionella Growth Potentials. The chart was excerpted from the 2021 IAPMO UPC.