Are you planning to reopen your premises? Then you’ll need to take steps to reduce the risk of Legionella (Legionnaire's disease)

Are you planning to reopen your premises? Then you’ll need to take steps to reduce the risk of Legionella (Legionnaire's disease)

Many businesses across the UK will be preparing to reopen and allow staff to return to work as lockdown restrictions ease. However, employers, the self-employed, and landlords must take steps to identify and control the risk of Legionella before employees and the public re-enter their premises.

What you'll need to do before you reopen

You should review your risk assessment to ensure you can manage any legionella risk before you start using the water system in your building. If the water system was in use during the lockdown, then continue to take appropriate measures to prevent the spread of Legionella.

The Health & Safety Executive (HSE) has published guidance on how to reduce the risk of Legionella when reopening buildings that have been temporarily closed.

What is Legionella?

Legionella is the bacteria that causes Legionnaire's disease. During the lockdown, the water in the water systems of unoccupied buildings may have become stagnant, providing Legionella with suitable conditions to multiply and spread, posing a significant risk to health. 

To find out more about Legionella, click here.

Controlling Legionella in hot and cold water systems

Hot and cold water outlets should be flushed out every week if they haven't been used regularly to prevent water stagnation.  If you can't do this yourself, seek the help of someone who understands the risk and can ensure your water system is cleaned (if required) and disinfected before you reopen the building.

It is important to monitor the temperature

Temperature control is the primary method of limiting the spread of Legionella in hot and cold water systems. However, you may also want to use biocides, such as chlorine dioxide and copper/silver systems.

For more guidance, read:

Controlling Legionella in cooling towers and evaporative condensers

You should check that cooling towers and evaporative condensers are functioning correctly. Trained personnel should also be on hand to carry out essential checks and monitoring and ensure chemical supplies are maintained and systems are dosed regularly.

Contact your water treatment company if you need help stopping any of these systems.

If your cooling tower or evaporative condenser is going to be out of operation for up to a month, then you’ll need to isolate fans and circulate water treated with a biocide around the system for at least an hour each week.

Using biocides and other chemicals

Biocides, such as sodium hypochlorite, bromine donors or non-oxidising biocides, are typically used in cooling towers or evaporative condensers.

If you're unable to source certain biocides, then there are authorised alternatives you can use that are equally effective. Your supplier can advise you on which products you can use. If you're still unsure, contact the HSE at:

As well as biocides, you can use flocculents, biodispersants, anti-foams, algaecides, corrosion inhibitors and scale inhibitors to run an effective water treatment programme. As an alternative to scale inhibitors, you can use a water softener to reduce limescale build-up. However, this method may not be practical in larger water systems.

Additional methods to control Legionella

Hydrodynamic cavitation, ultrasonic cavitation and the TiO2 advanced oxidation process will also manage Legionella in cooling towers, although these methods may not suit all systems.

Replacing cooling towers and evaporative condensers

You can also replace smaller cooling towers and evaporative condensers with dry coolers or dry/wet coolers. These alternative systems require little or no chemicals to operate safely. Do bear in mind though that they can involve significant capital investment and a long lead time to set up.

For more guidance, read:

Changing your Legionella control methods may pose a risk to operators

If you decide to change your control methods or strategy, you may be exposing operators to additional risks. For example, moving from an oxidising biocide to isothiazolinone may introduce a new skin sensitisation risk. According to the HSE, you should review your risk assessments for Legionella and COSHH and controls and increase the level of monitoring during the commissioning of any new control methods.

Personal protective equipment (PPE) required for cleaning water systems

You'll need to use respiratory protective equipment (RPE) that provides an assigned protection factor of at least 20 when cleaning a water system.

However, because of the COVID-19 outbreak, disposable RPE - such as FFP3 respirators used by health workers - may be in short supply. If the RPE you normally use is unavailable, you can source alternatives so as long as they are suitable for workers and the task at hand.

Alternative RPE may include:

  • a reusable half-mask or full-face respirator fitted with a P3 filter
  • a powered respirator and hood class TH2 or 3
  • a powered respirator and close-fitting full-face mask class TM3
  • an air-fed hood or full-face mask supplied with breathing quality air.

Find out more about using respiratory protective equipment at work (HSG53).

Getting specialist help during the lockdown

In some instances, you may need a specialist to help you identify and implement suitable controls for Legionella, and this may prove difficult during the lockdown. If you're unable to hire someone with the appropriate knowledge and authority to oversee the implementation of risk controls, you must consider shutting down your water system until you can.

The following professional associations have published guidance that may help you comply with the relevant health and safety regulations.

The Legionella Control Association has published guidance on managing water systems during the coronavirus outbreak.

The European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Study Group for Legionella Infections (ESGLI) has also published guidance for managing Legionella during the coronavirus outbreak that you may find useful.

The Chartered Institute of Environmental Health has published guidance on legionella risks during the lockdown and reopening safely (PDF)- Portable Document Format.

The government has also published guidance on managing school premises during the coronavirus outbreak (which includes controlling risks associated with Legionella).

Contact us

For further advice and guidance regarding our specialist insurance services for the property sector, please contact a member of our property team.