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Technologies for legionella control in premise plumbing systems

By the US Environmental Protection Agency

Water, Sewage and Effluent reproduces this summary in the interest of plumbers and engineers understanding their critical role in safeguarding the health of people. They make the design happen, and any deviation from standards and legislation is irresponsible, as such action will result in the cultivation of waterborne diseases.


Editor’s comment

The Legionella Action Group has just released a report on the outbreak of legionnaires’ disease occurring in South Africa, which we will publish in the next issue. The point is that a disease that we thought was long gone has returned. Let us hope that the authorities, designers, planners, legislators, and installers do not wait for an epidemic to occur before applying two simple rules: (1) Ensure that standards are applied; and (2) Forget any shortcutting in favour of profit and at the expense of the public, which we all purport to protect, except for unqualified professionals, plumbers and unscrupulous suppliers.

The US Environmental Protection Agency (EPA) developed this document because it recognises that many species of the genus legionellaare a public health threat. The EPA recognises that many facility managers are choosing to install treatment systems to prevent or mitigate legionellagrowth in their premise plumbing systems. The target audience for this document includes, but is not limited to, primacy agencies, facility operators, facility owners, technology developers, and vendors.

This document summarises peer-reviewed scientific literature, reports from nationally and/or internationally recognised research organisations, and guidelines and standards from nationally and/or internationally recognised organisations. The reviewed literature characterises the effectiveness of different technologies that may be used to control legionellagrowth in premise plumbing systems. Particularly, it focuses on premise plumbing systems of large buildings, such as hotels, hospitals, schools, and other buildings with complex plumbing infrastructure.

The EPA expects this document will improve public health protection by helping the target audience make better informed, science based risk management decisions to control legionellagrowth in buildings.


Legionellais a bacterium that can be found throughout the world, mostly in aquatic and moist environments, such as lakes, rivers, groundwater and soil. The infection caused by legionellais known as legionellosis and occurs primarily in two forms:

  • Legionnaires’ disease, which is a type of pneumonia (Fraser et al., 1977).
  • Pontiac fever, which is a milder flu-like illness without pneumonia (Kaufmann et al., 1981; Glick et al., 1978).
  • Risk management approaches (including temperature control)
  • Chlorine
  • Monochloramine
  • Chlorine dioxide
  • Copper-silver ionization
  • Ultraviolet light

The disease can be acquired by inhaling or aspirating aerosolised water or soil (potting soil, compost soil) contaminated with legionella(Travis et al., 2012). No infection associated with animal-to-person contact, consumption of contaminated food, or ingestion of contaminated water has been reported. Only one probable case of person-to-person transmission has been reported and it occurred in Portugal (Correia et al., 2016).

While anyone can develop legionnaires’ disease, some common risk factors for developing an infection include the following: age (>50 years), gender (male), smoking habits, existing lung conditions (for example asthma, chronic obstructive pulmonary disease), previous use of beta-lactam antibiotics, immunosuppressed or immunocompromised status (such as persons receiving transplants or chemotherapy; those with kidney disease, diabetes, or AIDS), and recent surgery or intubation (Health Canada, 2013; Viasus et al., 2013; Newton et al., 2010; WHO, 2007; Stout and Yu, 1997). The percentage of fatalities from reported cases of legionnaires’ disease increased with age (>50 years) and showed a similar pattern for males and females (ECDC, 2016).

Hospitalisation costs due to legionellosis in the United States are estimated at USD433-million per year (Collier et al., 2012). Fatality rates are estimated to be 5–30% (Kutty, 2015). The costs associated with loss of productivity and deaths are not included in these estimates and are likely to be significant. Between 3 000 and 4 000 cases of legionellosis are reported to the United States’ Centres for Disease Control and Prevention (CDC) each year. However, the actual number of hospitalised cases is estimated to be between 8 000 and 18 000 (Kutty, 2015; CDC, 2012; Marston et al., 1997), since many cases of pneumonia are empirically treated with antibiotics and never tested for legionella(CDC, 2011; Marston et al., 1997).

Legionellahas been found in public water systems. Environmental conditions and processing of the water once it enters a building can lead to the growth of legionella, which could result in increased risk of infection. The CDC has identified environmental conditions within premise plumbing as the leading cause of the legionellaoutbreaks reported between 2009 and 2012 (CDC, 2015; CDC, 2013).


The purpose of this document is to summarise the current body of knowledge on the effectiveness of different approaches to control legionellagrowth in large buildings.

As a result of legionellaoutbreaks and the potential for legionellato grow in premise plumbing of buildings, many facility owners or operators have decided to take measures to control or mitigate legionellagrowth. This document summarises information on several legionellacontrol technologies, including:

This document provides information on other control technologies that are often used for emergency remediation: superheat-and-flush, shock hyperchlorination, and point-of-use filtration.

A summary of the literature for each technology is provided. The summary includes information about the effectiveness of the technology against legionella, potential water quality impacts that may result from using the technology, and operational considerations.

This document describes different type of studies, which include laboratory, field, premise plumbing, and distribution system based studies. The results from the different type of studies may not be directly comparable to one another given the differences in experimental conditions.

Discussions of legionellacontrol issues related to cooling towers and other systems within the building that do not deliver water for human consumption are not within the scope of this document. The EPA defines human consumption as “drinking, bathing, showering, hand washing, teeth brushing, food preparation, dishwashing and maintaining oral hygiene”.

The next issue of Water, Sewage and Effluent will look at occurrence and risk, as well as the regulatory and enforcement context.

For more information about the Legionella Action Group, contact Rob Stewart on +27 (0) 11 489 8578.



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