ance after the outbreak at the VA hos- pital in Pittsburgh. However, the VA Pittsburgh hospital was never in com- pliance with the recommended tem- peratures in the 2009 VA Directive. The tepid temperature range of 85 F to 110 F (29 C to 43 C) clearly stands out in this appendix as the range with the highest Legionella risk. It is well-documented in numerous guidelines and standards as the high- est risk range for Legionella growth and should be avoided when possible. Some plumbing codes and health- care guidance recommend maintain- ing hot water at above 120 F (49 C) in the circulating system and reduc- ing down to 110 F at the fixture with point-of-use (POU) mixing valves. However, there are risks associated with such valves. ASHRAE Guideline 12 identifies Legionella growth poten- tial risk related to POU mixing valves in multiple sections of the document. The Illinois Veterans Home in Quincy, Ill., after its 2015 outbreak, set its water heaters to above 150 F (66 C), maintained greater than 130 F (54 C) in their supply and return lines, and installed POU mixing valves at all sinks, lowering the temperature to less than 110 F (43 C). Under this protocol, even with extensive daily flushing of each fix- ture, the veterans' home proceeded to experience additional outbreaks in 2016, 2017 and 2018. This should not be surprising as the water tempera- ture at all sinks, from the POU mix- ing valves to the faucets, was main- tained constantly in the tepid, high Legionella -risk temperature range. Throughout the United States, municipal supply water is treated with disinfectant, typically chlorine or chloramine. Municipal supply water in the tepid cold temperature range of 77 F to 85 F (25 C to 29 C) is com- monly found in many parts of the South and Southwest. This water has a relatively low risk for Legionella growth because the cold-water supply will typically include very low total bacteria counts and significant levels of disinfectant residual. Likely one of the main factors resulting in noticeably higher per cap- ita Legionnaires' disease rates in the Northeast in comparison to the South and Southwest - where it would be
38/Plumbing Engineer June 2021
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Legionella Throughout the United States, municipal supply water is treated with disinfectant, typically chlorine or chlora- mine. Municipal supply water in the tepid cold temperature range of 77 F to 85 F (25 C to 29 C) is commonly found in many parts of the South and Southwest.
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