You probably already know that it is a legal duty of most landlords and business owners to carry out a regular legionella risk assessment. This is to identify and assess any risk posed by possible legionella exposure through their water system. However, you might not know how legionella testing fits into this legislation. Read on to find out how often legionella tests are advised for different water systems, why additional tests might be recommended and how legionella tests are carried out.

What is Legionella?

Legionella is a bacteria that can grow in water and moist soil. When water systems allow debris to build up, water to stagnate or when water is not stored at safe temperatures, legionella bacteria can rapidly multiply.

People can develop illnesses through inhaling water droplets/aerosols inhabited by these bacteria. The most common are Pontiac Fever and Legionnaires’ Disease.

While most exposed healthy people do not get sick from legionella, Legionnaires’ disease, in particular, can be life-threatening to those with weaker immune systems. Among those most at risk include individuals over the age of 50, those undergoing medical treatment such as chemotherapy, and people with underlying illnesses like diabetes.

legionella bacteria in testing lab

How Often Should Legionella tests be carried out?

You will often be informed of the recommended period for legionella testing in your building as part of your legionella risk assessment – particularly if an issue is found which requires monitoring.

According to the HSE, testing should be carried out at least quarterly for open systems such as evaporative condensers and cooling towers.

In many cases, testing is not required for domestic hot and cold water systems. However, it may be recommended where there are uncertainties about the safety of the water system after a risk assessment. An example could be if there is doubt over whether the water is consistently being stored at a safe temperature.

There may be other circumstances where more frequent testing is required, such as if there has been a suspected case of legionnaire’s disease in the building. Regular microbiological monitoring may also be appropriate if the building is used as a care home, hospital or otherwise occupied by those who are particularly vulnerable to Legionnaire’s Disease.

More details about this can be found on the HSE website.

What happens during a Legionella Test?

Those taking water samples should ensure that they meet the Code of Practice laid out in BS7592- Sampling of Legionella Bacteria in Water Systems. This document sets the standard for how samples should be taken and stored and covers the protocol for neutralising water treated with biocide. Depending on the findings of your last risk assessment, they may wear protective equipment.

Several samples will usually be taken at different points to show that those samples truly represent the water in the entire system. The exact number of samples required will depend on the size and complexity of the system.

Usually, samples are taken from tanks, outlets and any parts of the system considered to be high risk- such as pipes where water may be stagnating or the warmest area of your cold water storage tank. Once these points are identified, they should be noted down so they can be used for future tests to maintain consistency.

The HSE state that water samples for legionella should be tested by a UKAS-accredited laboratory. Once your samples arrive at the lab, they will be tested over approximately 10 days. You will be notified when your results become available.

Rapid tests which can produce results within two days are also available. While these can be useful as a negative screening tool, the positive results are not always successful indicators of how high-risk legionella growth has become. For this reason, they are recommended as a complimentary tool rather than as a replacement for traditional legionella testing.

building water system being tested for legionelle

What will happen if Legionella is found in my water system?

The action you will need to take after your system tests positively for legionella bacteria will depend on the specifics of your results and the persistence of the colony.

If extremely low levels of legionella are found in your system, it’s often recommended that you should continue to focus on maintaining the control systems currently in place.

When low levels of the bacteria are found, more frequent sampling is usually required. You may also need to reassess the current controls and water treatment systems in place to bring your system back to a lower risk level.

If high levels of legionella are found, or if low levels are persistently found even after some intervention, then immediate action is needed. Your risk assessment should inform you what corrective action is required. Additionally, you should add or increase the amount of biocide in the system and resample 48 hours after implementing your corrective methods.

Who should carry out Legionella Testing?

While there isn’t a legal need to hire a professional to carry out legionella testing, there are many benefits.

When calling in the services of a water treatment company, such as Glacier, you can feel confident that the sampling is being carried out by a competent person with the full range of skills and knowledge necessary to assess the safety of your water system.

By using Glacier’s microbiological sampling services, you can also be sure that the testing is carried out following the LCA Code of Conduct to give you the most accurate results possible.

We also guarantee that all microbiological samples are taken, transported and analysed under UKAS accredited conditions.

Contact us today to discuss how we can help you to protect your water system.