The HSE ACOP (Approved Code Of Practice) L8 states that a suitable and sufficient assessment is required to identify and assess the risk of exposure to Legionella from work activities and water systems. A Legionella Risk Assessment involves visit by a trained assessor. The objective is to identify any areas where the bacteria may find suitable conditions for growth. A written report is then produced detailing the findings of the assessment, together with recommendations for remedial actions to reduce the current level of risk. The assessment takes into account the following factors:

• Water Temperature
• Water Stagnation
• Potential for Aerosol Formation
• Heat Gain / Loss
• Condition of the Water
• Condition of the Water Service and the Water System as a whole.
• The Susceptibility of Exposed Persons

The risk assessment should be reviewed regularly and whenever there is reason to believe the original assessment may no longer be valid, for example when additions or alterations to the plumbing system have taken place.

Water system disinfection

This process can only take place when a risk assesment has been completed and any remidial work is completed. There is no point in disinfecting a system where there are areas where stagnant water can lay in un used sections of pipe or a water tank can become contaminated due to a missing lid or an unscreened overflow.

The system is flushed to remove any debris and the tank is scrubbed and then flushed again. after this chemical disinfection can take place.

After the disinfectant has been left to do its work the system is flushed to remove any chemicals in the system. Samples are then taken and sent away to a water testing laboratry where the presence of leigonella bacteria can be tested, this can take up to 3 weeks.

When the results are returned the effectiveness of the disinfection process can be determinied. If the results show an un acceptable level of bacteria the system will have to be re disinfected this is rare and only occurs in extreme cases.