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Legionella Testing

Legionella Testing

What is legionella testing?

Legionella testing involves sampling the water in water systems to see if it contains legionella bacteria. 


When do I need to carry out legionella testing?

Legionella testing should be carried out when there are any potential problems with your water systems. Water samples are taken if your water temperatures are out of control and your water system is not maintaining temperatures. For example, if the cold water is constantly running above 20 degrees, if the hot water is running below 50 degrees, or if the condition of the water raises concern, you need to take water samples. If you use thermostatic mixing valves (TMV), the hot water temperature will be lower to prevent scalding, and in this instance, water temperature would not be an indication that samples were needed.


If a building has been partially or completely shut down for a sustained period of time, legionella testing should be carried out throughout the entire building to validate the system. During periods of shut down, all water outlets that aren’t used at least once a week need to be flushed, to flush water through the system and prevent stagnation.

In some cases, water samples will be taken and tested for legionella as part of a legionella control programme. This isn’t a legal requirement, but it can be included as an extra precaution when requested.


What is the process for arranging legionella testing?

When you contact us regarding legionella testing, we’ll arrange the testing for you as quickly as possible. We aim to respond to all queries within 24 hours, and we’re aware of the need to move quickly, especially if you are calling regarding a school, hospital or building used by vulnerable people.


The first question we’ll ask you is whether there is a legionella risk assessment in place. If you don’t have one in place, don’t worry, we can undertake one for you. It is a legal requirement to have a completed legionella risk assessment. Your legionella risk assessment will give us all of the information we need to understand the scale of your building, the type of testing you require, and to provide you with a quote for legionella testing. Your legionella risk assessment will identify: all of the assets on your systems, the size of your system and the number of outlets around your building.
















When will I get the results from legionella testing?

Once your water samples have been sent to the laboratory, it can take up to 14 days for each sample to grow. Growing legionella is difficult and it can be a very long process. For this reason, you’ll receive interim notifications regarding the status of your sample on days 3, 7 and 10. If the lab thinks that the result of any of these samples indicate the presence of legionella, they will send you an interim reading.


At Dakro, we act on interim positives rather than waiting for the final result. If there’s a count of 1,000 on day 5, by day 14, the count will be even higher. By acting on interim positives, we are able to get straight into looking at water treatments for your system to identify the problem and generate risk control actions and remedial work.


What strains of legionella require water treatments?

There are about 75 different strains of legionella bacteria, and all vary in how harmful they can be. At Dakro, we will act on the positive result of any species of legionella.


How long does it take to get rid of legionella if I have received a positive result from legionella testing?

There’s no ‘one size fits all’ approach to legionella that will give you a definitive answer regarding when your legionella tests will turn from positive to negative. The time it takes will depend on your specific system and circumstances so it’s impossible to give a time scale. 


What do I need to do if I receive a positive legionella test?

At Dakro, we run through a range of water treatment processes to ensure we cover all bases and get rid of any legionella bacteria as quickly as possible. We’ll start with one sample, then widen the search to more samples, and use chemicals to disinfect your system. After disinfecting your system, we’ll take samples 48 hours later. Often, this will be enough to remove legionella bacteria, but sometimes, we may need to widen the net of samples and look at your risk assessment in more depth to find the root cause.


HSG274 part 2 has a table that lists the steps we will take depending on the extent of your positive result. 0 - 100 means you don’t have to do anything, however Dakro’s approach is to make you aware of this level and suggest possible action to eradicate the problem. 100 - 1,000 requires a specific set of actions, and 1,000 plus requires an even longer list of actions to be covered.


How do I know if Dakro is able to carry out legionella testing for my building?

No building is too big or too small for our team, and we’re flexible to ensure we provide our customers with testing to suit your specific needs. 

Where will my legionella test results be recorded?

Our customers have access to a portal which will show you real time results whenever you need them. We’ll email results through to you stating whether no action is needed if the test is negative, or, in the case of a positive result, to provide an action plan for the future. Results can also be kept in a physical log book that we can provide. The log book is part of the legal compliance process and in accordance with HSE requirements, records must be kept for at least 5 years.

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