Why is Legionella Flushing Important?

The water safety specialists at Water Treatment Services highlight the benefits to be gained from the regular flushing of unused or little used water outlets in the battle to control legionella.

The article explains what legionella flushing involves and how it works to keep water systems safe to use. It goes on to consider how those responsible for the safety of water systems identify outlets that need regular flushing, it explains how to flush correctly, it covers the essentials of record keeping, and the importance of training and competence when flushing.

How to keep legionella under control?

It’s almost impossible to completely remove Legionella bacteria from manmade water systems. However, it is straightforward enough to keep it at bay – to keep the bacteria below danger levels so no one comes to harm.

There are various techniques we can use to help minimise the presence of legionella in any hot or cold water system. One of these is a process known as flushing. It is important to understand what we mean by flushing and how it can help the overall management of Legionella bacteria in any building or process that uses water.

What is legionella flushing?

Legionella flushing is a popular technique used to control the stagnation of water, a condition known to promote the growth of legionella and other bacteria in engineered water systems. Most commonly, flushing involves running the water from little used outlets including hot and cold taps, showerheads, through shower hoses and other water outlets for at least five minutes.

How does flushing work?

The idea behind regular flushing to control legionella is simple. Most buildings have water storage vessels or outlets (taps and showers) that are less frequently used than others. Think of a hospital or care facility where some rooms are commonly used and others far less so. There may be bathrooms with showers that are in regular use, while others are only occasionally used.

Implementing a regular flushing regime will reduce the risks from legionella in your water systems …

A legionella flushing regime would identify these outlets (showers, taps, and so on) and ensure they are flushed through regularly to prevent stagnation of the water inside the outlets. This simple task involves turning on the shower, tap, or other outlet and leaving it to run water through for a few minutes at pre-agreed intervals.

Regular flushing of water outlets could also be used following a temporary shutdown or mothballing of a building. The most obvious example here is during the COVID-19 lockdowns. Lots of buildings stood empty for many weeks, even months in some cases. The water in the buildings was not in use, so the issue of stagnant water, disused outlets and pipework, and lack of regular cleaning routines may have arisen in some buildings. If those buildings were reopened without first being checked, including the use of a legionella flushing regime, the potential danger of legionella being present would be much higher.

How to identify water outlets that need regular flushing?

The UK’s Health and Safety Executive determines that any water outlet used just once a week or less should be considered as a “little used outlet” and would benefit from a regular flushing regime. Therefore, it is important to make sure you are aware of how often each part of the water system is used in your building, as this will allow you to spot areas that may encourage stagnation.

The purpose of flushing is to keep the water in the system moving. This does not need to be constant, but it does need to be regular enough to prevent certain things from happening. Firstly, legionella prefers and can more easily multiply in stagnant water. So, when a portion of the water system doesn’t get regular use, the water will sit in the pipework. Secondly, this also makes it easier for biofilm to form inside the pipework which will allow the bacteria to more easily colonise the system. Biofilm will also protect the bacteria making it much harder to remove.

You should also clean and de-scale showerheads and hoses at least every three months …

By adopting a regular flushing regime, it is possible to minimise the risk of legionella colonising the water system, which in turn will help to keep people safe.

Who is best placed to identify little used outlets?

It makes sense that the individuals responsible for conducting the flushing process may not be the same individuals as those who best understand how the water system is used. For example, in a hospital, those working in specific departments will know which outlets get regular daily use and those that do not. These people can better inform those responsible for flushing outlets, giving them the information required to identify which ones need regular attention. Similarly, if the use of a specific area changes, and in turn so does the use of specific taps or other outlets, this information can be brought to the attention of those conducting the legionella flushing process.

How to flush taps and showers for legionella?

In addition to your flushing regime it is also good practice to try and reduce the risks from stagnant water as much as you can. One good way to do this is by identifying dead legs and dead ends in pipe-work, which should always be removed as soon as possible.

Little used water outlets which can include showerheads and taps that can’t be removed should be thoroughly flushed at least weekly or more often if the legionella risk assessment calls for it.

To flush unused or infrequently used water outlets effectively you should run the water from both hot and cold supplies through taps, showerheads and shower hoses for at least five minutes. You should take suitable safety precautions when doing this.

You should also clean and de-scale showerheads and hoses at least every three months. Cold-water storage tanks should be cleaned periodically and water should be drained from hot water cylinders to check for debris or signs of corrosion.

Should some outlets be flushed more than others?

Yes, certain water outlets should be flushed more regularly … this is likely to apply in some scenarios. If we continue with our hospital example, there could be areas that are more prone to having people with health conditions that put them at greater risk of contracting Legionnaires’ disease. The water outlets they are most likely to use should therefore be flushed more often, reducing the risk factors from legionella still further.

Keeping records of your legionella flushing programme

Keeping records of what you do is an essential tool in helping you stay on top of your legionella flushing regime. We can see just how important it is to maintain a consistent regime, and keeping notes of which outlets have been flushed, when, and who performed the process is important. Not only does it act as evidence of measures taken but it also gives you a place to record any adjustments to the programme.

The importance of training and expertise when flushing

Flushing can and should only be done by those with a clear understanding of what is required. Proper training is essential for this to be effective. The uninitiated may select the wrong outlets to flush, or they may not perform the job properly which could create a false sense of security.

The alternative – and a more practical route to take in many cases – is to hire an outside team of experts to perform the job. The building owner or manager (the duty holder or responsible person) is still ultimately responsible for the safe running of the water system. However, with experts on site to help manage and run the legionella flushing regime, there is far less chance of anything going wrong that could jeopardise the health of those using the building.

Expert Water Treatment and Water Safety Solutions

Water Treatment Services provide a comprehensive range of water and wastewater treatment, water quality analysis, consultancy, and water engineering solutions to support business owners and those responsible for the safe and efficient operation of water systems in the workplace.

Contact us today to learn how our water treatment specialists can help you manage your water systems, maintain regulatory compliance, and ensure safe, reliable performance.

With offices in London serving the South and South East England, Manchester (North West), Birmingham (Midlands), Bristol (South West England and Wales), Leeds (North and North East), and Glasgow (Scotland), supported by regional teams of highly trained technicians and engineers, we deliver specialist consultancy, water quality analysis, engineering support, and risk management solutions across the UK and internationally.