Legionella – Legionnaires Diseases.

In general, conditions, which permit legionella to proliferate and aerosol to be created, should be avoided.

Where, this is not practical, the risk should be minimised and controlled by reducing the release of water droplets and controlling the water quality. In relation to all water systems, proliferation may be avoided by: –

  1. Protect systems against external contamination, such as providing lids to storage tanks.
  2. Avoid water stagnation by keeping the pipe lengths as short as possible and tanks no larger than is necessary. Eliminate “dead legs” wherever possible.
  3. Maintain design temperature in both hot and cold water systems by providing efficient heating for hot water systems and adequate insulation for all pipes and fittings.
  4. Keep systems clean, tanks and other items need to be readily accessible for cleaning.
  5. Maintaining effective management of the services.

Control strategy features.

These have been identified by the “Health and Safety Executive” “Legionnaires’ Disease – The control of legionella bacteria in water systems” Approved code of practice and guidance reference L8.

  • Establish control level. The effective level of the control parameters (such as temperature, concentration of biocide etc) will need to be identified.
  • Achieve Control Level. The system should be capable of delivering and maintaining the effective level. (The rate of addition of some components may need to be varied as the rate of water usage changes).
  • Ensure Control Level. There should be some means of measuring the parameter to ensure that it is being achieved throughout the system.
  • Records. To be kept of the procedures/precautions.

Control Measures.

The traditional approach is that hot water should be stored at 60o C and distributed so that, after one minute of running a temperature of at least 50o C is attained at outlets. Cold water storage and distribution should be at 20o C or below.

At water temperature of 43o C and above there is a risk from scalding. Where a significant scalding risk has been identified the use of thermostatic mixing valves at baths and showers should be considered to reduce the water temperature. These need to be placed as close as possible to the point of use.

For most systems routine inspection and maintenance will usually be enough to ensure control if the following checks are made and appropriate remedial action taken when necessary.

  • Water temperature at calorifier / cylinders / hot water heaters.
  • Water temperature at a representative number of outlets.
  • Condition and cleanliness of storage tanks.
  • Condition of calorifier / cylinders / hot water heaters.
  • Condition of accessible pipe-work and insulation.
  • Operation of thermostatic mixing valves.

We can provide.

Legionnaires Disease, risk assessment as required by “The control of legionella bacteria in water systems” Approved Code of Practice and Guidance (ACOP).

Sampling for legionella and water quality, bacteriological sampling and inspections, checks, reports and analysis.

Information, instruction and training programmes, reviews of current practices, advice and re-assurance.

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Tuesday, June 9th, 2009 services