Dead legs, biofilm and Legionella
Dead legs are sections of water system piping with low or no flow due to system design and/or operation. Common examples include capped piping, closed cross connections, low point drains, cooling tower equalisation lines, bypass lines and out of service rooms or equipment. Intermittently operated faucets, showers, chillers, heat exchangers and pumps can also become dead legs depending on how long they are out of service.
Stagnant water in dead legs provides ideal conditions for biofilms to form. Any sediment accumulations also foster biofilm growth. Once established, biofilms, and associated microorganisms, provide a protective environment for any Legionella entering a building with the source water to multiply to high levels. Eventually, Legionella may be released into the bulk water and cause disease.
Dead legs in water systems can cause serious and costly problems. Design, operational and maintenance strategies must be employed to help manage biofilm problems where dead legs cannot be eliminated.
For practical advice on how to deal with deadlegs. Click here.