08 June 2020

Washroom considerations around Legionella

As lockdown measures imposed by the COVID-19 pandemic start to ease, many people will begin to return to commercial spaces that have been left unattended and unused for several months.

When locations such as offices and shopping centres are left empty for an extended period of time, there is an increased risk of a Legionella build up. Therefore, it’s imperative that the correct measures including flushing out water systems are carried out before staff and the public are allowed to use washroom facilities again.

 

What is Legionella?

Legionella refers to a group of free-living bacteria that live in the natural fresh-water environments and in soils such as moist potting compost. The low numbers in these environments are rarely dangerous to humans. They do however pose a risk in poorly controlled purpose-built water systems, both potable and non-potable, which means unattended washrooms are a prime target.

Contraction of Legionella can lead to Legionnaires’ disease, which is an increasingly common, severe and often fatal pneumonia that is particularly dangerous to individuals with weakened or compromised immune systems. As a significant, and often highly publicised, public health concern it is classified in many countries as a ‘notifiable’ disease, i.e. any disease that is required by law to be reported to government authorities.

The bacteria are relatively dormant at low temperatures, but multiply rapidly in warm temperatures — when they become dangerous for vulnerable individuals. This is why excellent controls must always be in place for building Water Distribution Systems (WDS).

In the wider environment, cooling towers and spa pools are the source of the majority of major outbreaks. Over 58 Legionella species have been described, of which at least 25 are linked to disease.

Where does the bacteria grow?

Legionella bacteria inhabit wet environments because of their ability to form biofilm, an intricate colony of microorganisms that can ‘glue’ themselves to inanimate surfaces such as metal and plastic.

The bacteria can ‘hide’ and proliferate in biofilm, which provides a safe harbour because the biofilm’s sticky ‘slime’ also protects the bacteria from heat and chemicals designed to attack it. As biofilm grows, sections will continually break off to contaminate water with free-living bacteria that can emerge in aerosols from water outlets such as taps and showers, as well as ‘seeding’ new biofilm colonies elsewhere in a water system.

Research shows that biofilm containing Legionella grows best in certain conditions:

  • Stagnant or slow-flowing water, such as that trapped in plumbing ‘dead legs’ or dead-end areas of a water system e.g. in water systems that have not been used for an extended period of time or where an out-of-use pipe, basin or shower has been blocked off
  • Where organic matter is present in a water system, providing nutrients for bacterial growth e.g. scale on taps. Legionella is commonly carried inside single-celled aquatic ‘host’ amoebae, which effectively serve as ‘Trojan horses’ to protect and distribute the organism around water systems.

 

What is Legionnaires’ Disease?

Legionnaires’ disease is an often-deadly pneumonia that has no specific clinical symptoms to set it apart from other pneumonias (atypical).

Legionnaires’ disease is contracted via inhalation of aerosols that may be released from a contaminated water source. Fine droplets containing sufficient numbers of bacteria can be breathed deep into the lungs where they replicate inside cells, this is where the Legionella develops into Legionnaires’ disease.

One thing to note regarding contraction is that person to person spread is possible but very rare.

The illness usually has an incubation period of two to ten days, but in rare cases can take up to two months to manifest, with severe cases leading to failure of multiple organs, sepsis and acute kidney injury. The overall death rate from Legionnaires’ disease is approximately 10-15%, which is why it’s so important Legionella prevention is carried out.

 

How do you combat Legionella?

Legionella bacteria are tough organisms to kill, making the bug challenging to control. It’s therefore vital that estates or FM teams have a rigorous control routine in place to ensure temperatures and conditions do not promote the bacteria or encourage its growth.

A comprehensive control regime for Legionella should include:

  • A planned, preventative maintenance (PPM) scheme for all parts of the water system, including thermostatic mixing valves (TMVs)
  • Regular maintenance of the plumbing system, ensuring water is flowing in all parts of the water system in order to prevent stagnation and the potential for build-up of biofilm
  • Flushing regimes to keep water moving through taps and wash basins, this is especially important after long periods of absence
  • Considered installation of point-of use (POU) filters on taps while contamination problems are being resolved
  • Measure to ensure any biocides (a chemical agent that kills bacteria) used in the water system are correctly specified and placed on the PPM testing schedule.
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