If you get a positive reading for legionella bacteria in your water system, there are a number of actions you will need to take.
The HSE’s Legionnaires’ disease Technical guidance Part 2 recommends that if the minority of results are returned with between 100 and 1000 colony-forming units per litre (CFU/l), the system should initially be resampled. If it is still positive, then an assessment needs to be carried out to identify remedial actions, and a review of your control measures must be undertaken. If the majority of the first sample results are between 100 and 1000 CFU/l, you will immediately need to review control measures and undertake a risk assessment to identify remedial action, including disinfecting the system.
If your sample has more than 1000 CFU/l, then you must resample the system and undertake an immediate review of control measures, as well as do a risk assessment to identify remedial action, including possible disinfection. Retesting needs to take place a few days after disinfection and at frequent intervals subsequently until control is achieved.
If you are in charge of a healthcare facility with vulnerable patients, you will need to investigate and resample water showing detection of legionella under 100 CFU/l, with all the subsequent measures detailed above.
After a positive test, it is likely that you will need to undertake corrective measures such as cleaning your water tank or chlorination. You will also need to do an assessment to determine any remedial works necessary, including looking at ways of improving the design of your water system in order to remove any areas that the bacteria will be able to grow in. For example, if there are redundant pipes, they can be removed completely. Alternatively, the water system may have to be redesigned in order to discourage stagnation, and other preventative measures carried out such as limescale removal, servicing mixing valves or insulating pipework. Or it could be something as simple as installing a new lid on your water tank.
The cost of the works will of course be dependent on what necessary actions have been identified in your risk assessment. This also applies to how long the work will take, but rest assured that our engineers will make sure that any disruption while the work takes place will be kept to a minimum.
Once the work has been completed, we will send you a detailed report of the works undertaken, along with photos which can be used as proof of work.