Dead legs in building water systems can cause severe problems, including persistent positive Legionella test results and an increased incidence of Legionnaires’ disease. Dead legs are sections of water system piping with low or no flow due to system design and/or operation. A basic understanding of dead legs, how to recognize them, and how to manage the problems they cause can help building owners reduce the risks associated with Legionella and other pathogens in their water systems. While the ideal solution is to remove the dead leg, the more realistic methods are a combination of design, operational, and maintenance strategies. Here are 7 common types of dead legs and some practical, effective methods to manage them.