Legionella risk assessment helps prevent Legionella pneumophila which is normally contracted by inhalation of affected water droplets, and not by drinking contaminated water.  Where water can be produced in a fine spray, for example, shower heads, cooling towers, spray taps, spa pools, swimming pools, fountains and vehicle washing equipment it is prudent to carry out a Legionella risk assessment.

Legal requirement for the Legionella risk assessment

Under the Safety, Health and Welfare at Work Act 2005 (No. 10 of 2005), every employer must prepare a safety statement which is based on an identification of the hazards and an assessment of the risks to the Safety, Health and Welfare of his / her employees. Environmental Efficiency can carry out the Legionella risk assessment.

Legionella Risk Assessment & Testing methods

The Legionella testing method is documented in UK HSE technical guidance document HSG 274 Part 2 and this method is followed by our experts in the matter.

A risk assessment is carried out first by checking temperatures of water outlets after being turned on for a specified time.  The potential for forming an aerosol or airborne droplets is also assessed.

Where a tap is considered at risk, a water sample is taken and set for analysis to an ISO17025 accredited laboratory.  A report is then written which constitutes the Legionella risk assessment.

Control of Legionella

The traditional method of legionella testing and control is by temperature. It is recommended that water is stored at temperature of 60oC and distributed so that reaches a temperature of 50oC within 1 minute of each outlet.  Where pipe runs are long, and taps used infrequently, taps may not reach the target temperature in time.  Point of use water heating may solve the problem.

For cold water taps, the water must drop down to 20C or lower in 2 minutes or less.  Often cold water taps are at risk as the pipes run parallel to hot water pipes thus heating the cold water.  If pipe runs are long, then the water at the tap may not drop below 20C quickly enough to ensure there is no risk.  Again, point of use water heaters may eliminate the need for long hot water pipes thus solving the problem.