How to deal with a positive Legionella test results at your premises?

Here on the Dynamika blog, we’ve talked a lot about the things you can do to prevent the growth of legionella and keep your business premises safe. But we haven’t spoken much about what you should do if your site ends up becoming the source of contamination. What should you do if Legionella testing uncovers evidence of contamination and you, therefore, receive a positive Legionella test? Read on…

What happens if there’s a Legionnaire’s disease outbreak?

First, let’s quickly cover what happens during an outbreak of Legionnaire’s disease; the potentially deadly condition caused by legionella bacteria.

If hospitals or medical facilities suspect even a single case of Legionnaire’s disease in one of their patients, the staff are required to notify their local authority’s health protection team (HPT).

In the case of an outbreak, this will lead to the convening of an outbreak control team (OCT) who will work to investigate the source(s) of the outbreak, enforce control measures, and handle communications regarding the outbreak (including public announcements).

Various officials and organisations can make up this OCT; but crucially, one of them is typically the Health and Safety Executive (HSE).

This is the organisation responsible for enforcing health and safety legislation; including the Health and Safety at Work Act, and the Approved Code of Practice L8 for legionella control.

If an outbreak is traced back to your premises, you’ll be ordered to implement emergency control measures to stop the spread. The HSE may also prosecute if they believe you’ve committed a serious breach of health and safety legislation; and the penalties for breaches can range from huge fines to imprisonment.

In other words, an outbreak can be extremely bad news for your business.

That’s why regular testing and inspection of your building’s water systems is so important for catching a potential outbreak risk early.

1. What to do if your legionella test is positive: step by step

Don’t panic. Finding traces of legionella can be worrying, but the mere presence of the bacteria doesn’t necessarily mean that you’ve breached health and safety legislation.

In any case, the issue of potential contamination needs to be carefully investigated and addressed; which is tricky to do effectively if your stress levels are through the roof.

2. Do you need to report a positive Legionella test to HSE?

In most cases, you’ll only need to report to the HSE – or your local environmental health department – if any staff members who have been working on or using the affected water systems are experiencing symptoms of Legionnaire’s disease. These include:

Flu-like symptoms
Chest pain
A persistent cough
Trouble with breathing
High temperature and feverishness

You’re required to report these cases under the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations (or RIDDOR). You don’t need to report the detection of legionella bacteria to HSE. However, depending on your industry and building type, you may need to report this to other relevant regulatory bodies.

How to deal with positive Legionella test results at your premises?

3. Consult your legionella risk assessment

Your first port of call should be your legionella risk assessment, which should indicate the correct procedures and remedial action to take to address the contamination. If your risk assessment has gaps, or you’ve neglected to fill one out, keep following this guide (but bear in mind that most of the advice is more generalised and may not address the particular control requirements for your premises and industry area). It’s a good idea to seek out a qualified legionella consultant to oversee the process, as they can help you interpret test results and recommend remedial actions.

4. Understand positive Legionella test results

Microbiological testing will identify the number of dangerous bacteria (or ‘colony forming units’, abbreviated as ‘Cfu’) per unit of water (typically litres, abbreviated as ‘l’). The HSE defines three thresholds for legionella detection in hot and cold water systems: Less than 100 colony forming units per litre (<100 Cfu/l) This means the amount of legionella bacteria is unlikely to pose any health risks for most business types, and so further action is not usually required. However, the presence of any legionella in a medical or healthcare setting (such as a hospital or care home) will usually warrant further investigation. Between 100 and 1000 colony-forming units per litre (>100 Cfu/l – <1,000) This could indicate low-level contamination of your hot and cold water systems, which may still pose a significant health risk. Over 1000 colony-forming units per litre (>1,000 Cfu/l) This indicates serious contamination of legionella, which needs to be tackled immediately.

5. Carry out a resample

You’ll typically need to take new water samples from your water system and carry out a second test.

This generally serves two purposes:

it helps to confirm whether the results of the first test were accurate (particularly if , and
by collecting samples from different points in the water system, the extent of the contamination across the system can be determined and the source of the contamination can hopefully be pinpointed.

With more information on the accuracy of test results and the likely source and extent of the infection, you’ll potentially be able to implement better control methods for preventing future legionella growth.

But before we get to that stage, it’s time to…

6. Disinfect the system

Disinfection of your water system should be considered if your test results sit in the >100 Cfu/l – <1,000 range, and should absolutely be carried out if they sit above the >1,000 Cfu/l threshold.

There’s a number of ways of doing this, but often the most suitable method is chemical disinfection via chlorination; dosing the system with chlorine to kill off the bacteria, followed by a neutralising agent to safely flush out the chlorine solution and return the water system to working use.

You’ll want to carry out subsequent resampling and retesting until the legionella has fallen below safe levels (or has been eliminated altogether).

7. Review your control measures

Take a look at your procedures for controlling legionella and identify how this particular contamination slipped through the net.

Do existing control methods simply need to be tightened? Perhaps resampling has uncovered a part of your water system that your risk assessment hasn’t addressed? Do unused or faulty parts of the system need to be removed or replaced?

Record your findings; and then crucially, make sure they’re implemented quickly. Your solutions won’t stop future outbreaks if they remain stuck on a to-do list!

Dynamika’s water experts offer complete legionella water testing via UKAS-accredited laboratories; as well as legionella risk assessments to help keep your staff and customers safe from harm. Call us on 03333 22 0800 or get in touch online to find out more.