When to Test for Legionella | Water Treatment Services

When should you test for legionella is one of the key questions which anyone with responsibility for the management and control of health and safety in the workplace, and in particular the delivery of safe water supplies asks. The simple answer would be to do whatever the UK’s safety laws require you to do as a minimum… and here we’ll explain more.

When is legionella testing required?

The regulator in this area, the Health and Safety Executive (HSE) set out in their Approved Code of Practice ACOP L8 and health and safety guidance HSG274 publications many aspects for the control of legionella in the workplace, including when legionella testing is required.

The ACOP L8 and guidance documentation are aimed at keeping people safe from the dangers of the potentially fatal condition known as Legionnaires’ disease.

Learn more about Legionnaires’ disease

Understanding your obligations to control legionella is essential

However, most people have never read the HSE’s ACOP L8 or HSG274 documents, probably because of their extensive technical detail.

They are not really documents which are designed for the lay person, but should be considered essential reading for those with responsibility for the maintenance and safety of water systems at work.

This could include business owners, landlords, health and safety managers, property and estates managers, the legionella responsible person and the appointed duty holder.

Download your copy of the HSE’s ACOP L8

When should you test for legionella?

We’re going to look at the HSE’s key documents highlighting the main issues relating to the requirements for legionella sampling and water testing.

Learn more about testing for legionella

One important point to note is that the requirement for testing for legionella doesn’t apply across the board. However, there are a number of circumstances when legionella testing is required and these include:

Control Issues
When there are doubts about how well the legionella control programme is working.
Temperature Control
The recommended water temperatures are not being achieved.
Chemicals
There are potential issues with the concentration of disinfectants used to control biological growth, including legionella.
Other Precautions
Other water safety precautions aren’t working effectively and could put people at risk.
High Risk
The property or facility is designated as “high risk” – this can include healthcare settings such as hospitals, care homes, nursing homes etc. where the people there are already ill or have weakened immune systems.

Other situations where testing for legionella is recommended

The HSE also sets out other examples of situations where testing for legionella is recommended and these include:

Chemical Control
In any operation that introduces a water system where biocides are used for treatment and when the water is stored before use.
The recommendation in this case is for monthly testing to start off.
Once you have confidence that your water treatment regime for disinfection or cleaning is working properly, only then can you look at reducing the frequency of legionella testing.
Out Of Specification
When you have set limits of tolerance in your water system, and these levels are consistently being breached.
Look at all aspects of the water system, including temperature and the concentration of disinfectant products.
As you try to bring the water system back under control, implement more frequent re-testing to make sure any changes implemented are effective.
Increased Risk
In areas which are at a higher risk from the growth and spread of Legionella bacteria, or where the people using the premises are more prone to developing illness, such as healthcare settings, hospitals or residential care homes.
Legionnaires Disease
Where an outbreak of Legionnaires’ disease has already occurred, and the water system is suspected or known to be the culprit.

Learn how testing your water for legionella can improve risk management

How, where and when to take legionella water samples

Each water system is different and you will have to look at its design, inherent risks and how it is performing to work out where to take water samples, and how many samples to take.

The key to any legionella sampling programme is to make sure that you are getting a representative sample of all of the water in the system.

… keep your hot water hot, your cold water cold, and keep it clan and moving.

Water samples should be taken from both hot and cold outlets rather than a mix of warm and cold water flowing through a mixer tap.

It’s good practice to label samples clearly with details of the outlet, the date and where they were taken from.

This procedure allows for easy identification once the legionella testing results are available.

Another recommendation is to “flush” the water system when taking samples.

This means taking the first sample immediately after turning the valve, shower or tap on – this is called a pre-flush sample.

Then leave the water running for at least two minutes before taking another sample for comparison – called a post-flush.

Recommendations for legionella testing

There are a range of recommendations about where you should aim to take samples of water for legionella testing and these include:

Risk Assessment
Any areas highlighted as being higer risk in your legionella risk assessment.
Water Temperatures
Any areas where water temperatures from the hot water feed are below 50 °C (55 °C in healthcare settings), or where the cold water feed temperatures are above 20 °C.
Out of Specification
Locations where levels of disinfectant used to treat the water are lower than your target specification.
Low Flow or Stagnation
Areas of the system where the water is not used often or is prone to stagnation.
This includes over-sized water storage tanks, areas of low flow, dead-ends and dead-legs in the pipework.

The dangers caused by dead-legs, dead-ends and stagnation

Dead-legs are sections of pipework which have no outlet – they have been islated for some reason or other.

This could be because there was previously a tap or shower which has been removed, but where the old pipe remains connected to the water system.

Many experts also label taps or pipes which are only used very occasionally as dead-legs or little used outlets.

These dead leg pipes and little used outlets allow water to pool and stagnate.

This can increase the legionella risks as the stagnant conditions provide the ideal environment for microbial growth.

Controlling legionella using water temperature – thermal control

Legionella bacteria thrives in temperatures between 20 °C and 45 °C.

This is why the HSE’s guidance recommends keeping hot water above 50 °C ( 55 °C in healthcare), and cold water below 20 °C.

Legionella thrives in temperatures between 20 °C and 45 °C

Put simply, you should keep your hot water hot, your cold water cold, and keep it clean and moving.

More guidance on water sampling

Although every water system is different, there are a few general guidelines to help you work out where to sample water for legionella testing.

Testing cold water for legionella

In cold water systems the sampling points can include:

- The point of entry (or the nearest outlet) where water comes from a private supply. Take samples here also if the temperature of the water coming from the mains supply is over 20 °C, or is drawn above that temperature from a water storage tank.
- Both the furthest and nearest outlets on each branch of the system, these are often referred to as sentinel outlets.

Testing for legionella in hot water systems

In hot water systems, samples should be taken at:

- The outlet at the base of the water heater, as long as the pressure is low enough to allow you to do this.
- From the furthest and nearest outlets on each branch of the system.
- From the furthest and nearest point on any loop which water circulates around.

Managing legionella for residential landlords and rental property

It is usually the responsibility of a residential landlord – not the tenant – to manage the potential risks from Legionella bacteria and Legionnaires’ disease in their property.

Under UK safety law it’s a legal requirement for landlords to conduct a legionella risk assessment and to take steps to control any risks identified in that assessment.

If a landlord has an empty property after a tenant leaves, the risk from legionella may increase because the water systems are left unused allowing the water in them to stagnate.

It is essential that landlords should know what to do to stop water stagnating in their water systems.

In general terms, this means making sure that the hot and cold water is flushed at least once a week to keep the water flowing and to stop any risk of stagnation.

If a landlord knows that their property is going to be unoccupied for longer periods, they could think about draining the water systems or paying someone to go in and flush through the system regularly.

This regular flushing will help to keep legionella in check.

What about Legionnaires’ disease at home?

When it comes to privately owned domestic or residential properties, there are no legal requirement to manage or test for legionella.

However, that doesn’t mean that home owners should ignore the risks from legionella entirely.

Learn more about legionella testing

There is lots of help and advice available for homeowners who wish to understand more about Legionnaires’ disease and water testing.

Expert legionella testing and risk management solutions

Water Treatment Services offer a range of legionella testing and water safety risk management solutions to support businesses and those responsible for the safety of engineered water systems in the workplace.

Our water safety experts can help you manage your water systems, maintain regulatory compliance and so keep people safe.

With offices in London serving the South and South East England, Manchester (North West), Birmingham (Midlands), Bristol (South East England and Wales), Leeds (North and North East) and Glasgow (Scotland), supported by regional teams of specially trained technicians and engineers we can offer specialist legionella risk assessments, training, water testing and other risk management solutions to businesses throughout the UK and Internationally.