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Legionella Bacteria eradicated from water tank - Case Study

Legionella bacteria was discovered within the hot water system of a communal residential building. All the hot water systems within the area were fed from a single 16 m3 Braithwaite water tank coated with a corroless paint system.The tank fed 3 calorifiers which in turn fed to numerous buildings. Sample results revealed that only one building had high levels of Legionella bacteria.

Due to high occupancy, Chlorination was not an option. Re-sampling was undertaken and a thermal disinfection was attempted but could not be held at high temperatures for a long enough period of time.

The first set of re-samples came back positive so a disinfection (using Supersil) was carried out. This was due to occupancy and the fact that the chemical used did not need to be flushed after the standing time had been achieved.

A new set of samples were taken and the system was flushed regularly to turn over the water until the sample results came back negative. The system will be closely monitored to checked performance in future.