Why is Legionnaires’ Disease a risk when I re-open my business?

Why is Legionnaires’ Disease a risk when I re-open my business?

Legionella bacteria in ideal conditions will grow, if you put legionella on an agar plate and incubate it for 7 – 10 days with a temperature range of between 20˚C and 50˚C, a colony will form of millions of bacteria that you will be able to see.

What is Legionnaires’ disease?

Legionnaires’ disease is a type of pneumonia caused by bacteria.

How do You usually get it?

By breathing in mist from water that contains the bacteria.

Where will I find it?

Legionella are relatively resistant to standard water disinfection procedures and, can occur in portable water (safe to drink; drinkable).

Legionella bacteria have been found in water distribution systems of:

  • Hospitals,
  • Hotels,
  • Clubs,
  • Public buildings,
  • Homes,
  • Factories.

The Health & Safety Executive’s HSG274 Legionnaires’ Disease: states that storage tanks, water heaters, pipework and components and associated equipment containing water” should be “designed to avoid water stagnation by ensuring flow through all parts of the system”.

You need to remember as the building has not been used for a period of time since closing the premises due to Covid-19 there is a risk that Legionella bacteria is present in areas such as outlets for example: – toilets, taps and showers  as they have not been used in an extended amount of time.

The Health & Safety Executive’s HSG274 Legionnaires’ Disease: Technical Guidance Part 2 states that any outlet “not used for a period equal to or greater than seven days” should be classed as a little used outlet

Little Used Outlet

Due to the workplace being closed for an extended length of time, outlets have not been regular and frequent used and so there for are temporarily out of use these are classed as little used outlet.

The definition of “infrequent use” may vary between applications and will depend not only on frequency and duration of use, but also other risk factors, such as water temperature and the vulnerability of the population.

So what to do?

When you first re-enter the work premises, run the shower and taps.

Taps: –

When flushing taps, run each one for at least five minutes. Turn the water on slowly so you do not splash it, thus releasing water droplets into the air this will flush through any bacteria.

Showers: –

run the water from both hot and cold supplies through the shower hose for five minutes. To ensure no spray escapes run it through a bucket of water.


The showerhead should be removed, and the shower run for five minutes. The showerhead should be disinfected before being re-fitted. Showerheads should be regularly disinfected about four times a year.


Flush the toilets several times ensuring the lid is down preventing the release of water droplets into the air.


Raise the temperature to 60°C or higher. Temperatures above 60°C will kill Legionella bacteria so make sure that the temperature of the hot water in your boiler/cylinder is set at a minimum of 60°C. Beware of burns and scalding. Legionella can survive in low temperatures, but thrive at temperatures between 20°C and 45°C.

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