The Environmental Protection Agency (EPA) has an established Maximum Contaminant Level Goal (MCLG) of zero for the presence of Legionella in drinking water.
The City of Napa water system meets this non-enforceable guideline through compliance with EPA’s Surface Water Treatment Rule, which requires water systems to filter and/or disinfect water so that microorganisms are removed and/or inactivated.
The City of Napa monitors it’s residual disinfectant in the distribution system. Even with these processes, however, small amounts of Legionella can survive, and, given the proper conditions, can colonize in on-premise plumbing systems.
Consequently, a key element for controlling Legionella is the design and maintenance of cooling towers and on-site plumbing systems to limit Legionella growth and aerosolization. Increasing the temperature of hot water systems and ensuring proper biocide treatment of cooling towers may limit exposure to Legionella.