Preventing risks of Legionella using continuously operated recirculating plumbing systems

Legionnaire’s Disease, a type of pneumonia, is caused by a bacterium called legionella pneumophilia which grows in the long-term stagnation of water, among other environments. Use of a continuously operated recirculating plumbing system such as our Tigris K1 can reduce risk of this bacterium. Read on to find out more.

What is Legionnarie's Disease?

Legionnaire’s Disease, a type of pneumonia, is caused by a bacterium called legionella pneumophilia. This potentially life-threatening disease is contracted by inhaling the bacteria within small water droplets, and while around 400 cases a year are reported in the UK, there are potentially many thousands of others misdiagnosed as flu. There are a number of causes which aid its formation.

These include:

  • Water temperature of between 20-50ºC, with the optimum temperature for legionella growth being 35ºC.
  • Long-term stagnation of water
  • A favourable biofilm – this is formed when groups of microorganisms adhere to each other on a material’s surface. Even perfectly hygienic potable water contains bacteria and the nutrients that fuel their growth, and biofilms develop in all water-conveying systems.

Continuously operated recirculating plumbing systems, also referred to as ring mains, provide continuous hot water on tap at a minimum of 60ºC (+/- 5ºC). Drawn water is replenished with an incoming fresh supply to replace it, meaning that hot water is always available at the tap. In addition to offering the convenience of instant hot water, the systems have significant health and safety benefits as a result of reducing the risk of bacteria build up by avoiding stagnation, and providing a constant high temperature.

Continuously operated recirculating plumbing systems such as our Tigris K1 provide faster distribution of hot water to the tap, which can also reduce water wastage and provide shorter output times. Such systems are popular in large environments where health & safety is critical, such as healthcare facilities and residential care homes.

Considerations for system specifiers

Specific components of a system will depend on a building’s size and nature and factors such as the number of outlets, inlet pressure, water quality and number of consumption units. An important consideration is biofilm minimisation by ensuring cleanliness during installation and start-up and reducing scaling and corrosion – via correct system design, materials choice and maintenance regime.

Material selection is key when designing a continuously operated recirculating system. Despite the fact these systems are easier to disinfect than others, the chosen material needs to be able to cope with thermal disinfection (at 70ºC), or chemical disinfection commonly used in large continuously operated recirculating systems. Examples of disinfectants used include continuous smaller measures of chlorine, or ‘shock’ disinfection in high amounts for a short period, often used in the case of a suspected bacteria outbreak.

Both methods of disinfection will affect the lifetime of a piping system, and selecting resistant materials is crucial. When specified, designed and installed correctly, continuous recirculation systems will deliver hot water quickly, efficiently and safely, helping to prevent bacteria growth into the future.

Learn more about Tigris K1

Tigris K1 is a multilayer pipe system designed for potable water and heating applications. It is ideally suited for installation on commercial projects such as educational establishments, apartment blocks and hotels. Learn more

About the author

Gabrielle Fletcher

Gabrielle joined Wavin in 2014 to work with the UK’s hot and cold product team. Her role is focused on the ongoing development of Wavin’s Tigris K1 commercial press fit plumbing system.

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