BS 7592:2022 Sampling for Legionella Bacteria in Water Systems
In this expert review the water safety specialists at Legionella Control International highlight some of the key changes to the updated British Standard BS 7592:2022, dealing with sampling for legionella bacteria in water systems.
The review looks at why it is important to examine the real reasons behind the need for sampling, and then goes on to consider the development of sampling plans, routine samples, outbreak investigations and how to compare the old and new standards.
A version of this story dealing with the updated BS 7592 for legionella sampling appeared in Legionella Control International’s newsletter. To get it in your inbox, sign up for free here.
What is BS 7592:2022?
BS 7592:2022 is a British Standard published in 2022. It sets out procedures to test water systems for the presence of legionella bacteria. It applies to engineered water systems such as hot and cold water systems, cooling towers, spa pools, and other water systems identified as a risk. It describes methods for sampling water from artificial systems together with monitoring techniques to support legionella control activities. It also clarifies techniques for the sampling of biofilms and sediments in water systems.
BS 7592:2022 revised
It may surprise you to learn that the last revision to BS7592 for legionella sampling standards was way back in 2008. It was more than overdue for an overhaul, and 2022 is the year that the rewrite was completed and published as BS 7592:2022. Here we look at the differences and why the new revision to sampling standards is so important.
It’s important to be crystal clear on why you are testing for legionella bacteria
Why are legionella samples being taken?
One of the key elements noted in this revised BS 7592 standard is that there should be a clear reason why water sampling for legionella bacteria is undertaken. There is no need for sampling to occur if the water system is working well and under control, especially if there have been no signs of contamination at raised levels, for instance.
However, two good examples of situations where legionella sampling would be required are as follows:
- The control scheme used to maintain the safety of the water system has failed.
- One or more people at greater risk of contracting Legionnaires’ disease are now using the water system but did not do so before.
Developing a legionella sampling plan
If either of these scenarios should arise, a plan for suitable legionella sampling should be created. If there is a large and complex water system, this may involve members of the Water Safety Group (WSG). For much smaller buildings where a responsible person is required to oversee things, they would be the individual to consider where best to sample the water supply.
It should be noted that while these two examples are just that, they are not exhaustive. Other risk factors may also be highlighted in the legionella risk assessment that could lead to sampling being required.
The idea here is that random sampling would not be suitable in this scenario. It is best to identify the specific points in the water system that should be tested. For instance, in the example of individuals at greater risk of infection, outlets in areas most used by those individuals would be ideal for water sampling and testing.
Additional guidance covering Legionnaires’ outbreak investigations
A number of new annexes have been added to BS 7592:2022, providing guidance for legionella bacteria sampling where an outbreak of Legionnaires’ disease has occurred. These annexes cover such locations as hotels, hospitals, and other healthcare settings. In each case, a plan for sampling should also reflect an up-to-date copy of the legionella risk assessment, as this plays an important role in the outbreak investigation approach taken.
The updated BS 7592 standard also provides further advice on new water system installations, along with information on refurbished buildings and possible differences in those water systems.
Updated advice for legionella sampling of water storage tanks
In some cases, smaller edits have been made to the BS 7592 standard, such as the new advice to refrain from opening potable water storage tanks. This was previously noted as dip sampling and was viewed as an acceptable way to go about it.
This approach has changed for the new standard. If water storage tanks require sampling, there are two preferred alternative routes to take that would not raise the risk of introducing foreign bodies such as dust into the tank.
1. Add a valve for sampling
The first recommended option would be to use a valve designed for sampling purposes.
2. Use the closest outlet
The second option would involve going to the water outlet closest to the storage tank.
These may be small changes, but clearly they can have a major effect on the situation, protecting the water system from unnecessary contamination while sampling takes place.
Routine water sampling
Routine sampling for legionella bacteria in water is also covered in the updated British Standard. Sampling of this nature should be taken before flushing (called pre-flush), although it also notes the importance of post-flush samples where water outlets that pose a greater risk are concerned. Again, the value of the legionella risk assessment will highlight these outlets where necessary. It further highlights that such outlets should be rinsed through using clean water following the sampling process.
How to review the new BS 7592:2022 standard
To be sure of spotting all the changes to the new legionella sampling standard, it is ideal to review the old one and the new one together. While some areas may seem to have only minor tweaks, it is clear these have been done with safety in mind. For instance, where previously we might have opened potable water storage tanks to sample the water inside, we now need to minimise opportunities for unnecessary contamination and identify the best place to do this without opening them. Many will undoubtedly find the annexes to be useful, along with the additional advice on sampling where a new water system is commissioned or an existing one recommissioned.
It has been 14 years since the BS 7592 standard was last reviewed, so this has been overdue for a review. The big focus on legionella sampling for a specific reason is clear here, and ought to be well received by those working as responsible persons or as part of a Water Safety Group. The standard arguably provides more clarity on many relevant testing topics. All those involved in water safety for a building or complex should read through the new standard as soon as possible, to ensure all measures are being met.
Leading legionella and water safety specialists
Legionella Control International are experienced legionella and water safety specialists supporting those responsible for the control of waterborne pathogens including legionella in the workplace. We help businesses protect their workers, customers and others from the dangers caused by water systems, helping them to meet their health and safety compliance obligations in this specialist area.
We are experienced in all aspects of legionella and water safety and deliver a full range of services including legionella sampling and water safety risk assessments. We also offer compliance auditing, water quality testing, City & Guilds training and other health and safety risk management services that help keep staff and others safe.
If you would like to speak with one of our legionella specialists about improving your risk management processes call us today on 0330 223 36 86 or contact us here …