At the first glance, guidelines may lead engineers and facility operators to conclude that controlling Legionella bacteria in plumbing systems can be accomplished long-term by simply raising water heater temperatures.
As with any solution that appears easy and cheap, it is important to check the fine print.
First, understand that water temperatures are just a small part of a comprehensive Legionella prevention program.
Second, understand the limitations of water temperatures in controlling Legionella. Increasing hot water temperatures may not be an option because of regulations. Mixing valves may help with Legionella control in some systems but not in others. And, reducing cold water temperatures may be infeasible or impractical.
Third, don't assume Legionella control based on temperatures. Even if water can be maintained within the temperature range typically recommended for Legionella control, the results for real plumbing systems will very likely be different than the results for the piping loops set up for the laboratory studies on which the recommended ranges were based.
Water temperature management must be given its proper place within a Legionella prevention program – no more and no less. Target temperatures must be set thoughtfully, achieved safely, and measured. As with the entire Legionella management plan, the effectiveness of water temperatures in controlling Legionella cannot be guaranteed and must therefore be validated rather than assumed.
For more on this topic, click on the article, "The Fine Print" (PM Engineer, October) on the free articles page.
For the important nuts and bolts details about setting and maintaining water temperatures and fixing water temperature problems, register for the online course, "Water Temperatures and Legionella in Plumbing Systems."