Legionella

What you should be doing if the building is still partially in use

You must first refer to your Legionella water risk assessment and written scheme for the premises. If the building is still partially in use you may follow your current controls and apply additional measures where necessary to keep the remaining occupants safe.

  1. Monitor
    Maintain your normal control regime so that the hot water is circulating throughout all parts of the system and flow temperature is maintained at above 60°C and the return on all loops is at above 50°C. Monitor water temperatures to ensure these temperatures are reached. The temperature should reach all outlets at above 50°C within 1 minute.
     
  2. Flush
    Flush gently (to reduce aerosols) all hot and cold outlets (showers and taps) at least weekly until they achieve the above temperatures. Where there is thermostatic mixer valve ensure the pipework feeding them achieves the same temperatures. Flush all WC cisterns, making sure that the toilet seat lid is closed when you do this, urinals, by-passes and any other points on the network.
     
  3. Disinfect
    For systems which are to be closed, where possible either drain and dry thoroughly, or disinfect so all parts of the system reach 50 parts per million free chlorine for 1 hour (or equivalent) as stated in your water risk assessment, flush through and drain.
     
  4. Document
    This should include reviewed and amended risk assessments, monitoring data and remedial actions, with evidence of the most recent person responsible who carried out the work, add time date and signature.
     
  5. Maintain
    You must then continue to adequately control Legionella within these systems.

What you should be doing if the system has been shut down

Draining systems down

Any system which is drained unless very small and simple will pose a risk when restarted as there will be remaining pockets of water and condensation which is sufficient to allow Legionella bacteria to grow.

Before draining, carry out a full system disinfection flushing through to all outlets to achieve 50 parts per million free chlorine or equivalent biocide for at least an hour. Then follow the below steps for when restarting the system. Do not just bring the system back into use without first taking the necessary measures to ensure the system is safe as this could expose people to Legionella bacteria. 

Where biocides are not used drain the system down and blow air through the system to dry as thoroughly as possible.

Restarting the system

It is important that the system is safe before it is brought back into use. When restarting, you should consider the following.

  1. Disinfect
    Disinfect the cold water system, flush though to all outlets to achieve 50 parts per million free chlorine or equivalent biocide for at least an hour checking that this level is achieved at the furthest outlets, top up when required.
     
  2. Flush
    Flush and refill the system to achieve maximum normal operating target levels of disinfection.
     
  3. Refill and reheat
    Refill and reheat the clarifier to 60°c and when it has been heated throughout, open the valves and flush through all outlets taking care to avoid any scalding risk. Water temperatures must reach and be maintained at 60°c.
     
  4. Monitor
    Monitor temperatures and biocide levels where applicable for at least 48 hours and then take Legionella samples from the sentinel outlets (the first and last taps). Adjust where necessary.
     
  5. Sample
    It is recommended that samples are taken 2-7 days following recommissioning and not on the day of disinfection. Follow-up samples may need to be considered as part of the recommissioning plan to ensure control is maintained.
     
  6. Re-open
    When you are satisfied the hot and cold water systems are under control then you can open the building. You will need to make sure that you keep documentation for inspection and follow the advice for other additional water systems or equipment.
     
  7. Maintain
    You must then continue to adequately control Legionella within these systems.

These steps have been taken from the guidance issued by the European Society for Clinical Microbiology and Infectious Disease Study Group on managing Legionella in building water systems. You must take into account that all water systems are individual.

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Leisure centres and health spas with spa pools, whirl pools and other systems

If spa pools have been taken out of use during this period of lockdown, those responsible should not forget the need to manage the risks from Legionella growth. This will also include water distribution systems feeding showers, kitchens and spas. The same risk factors apply to these systems as they with hot and cold water systems.

You must first refer to your risk assessment and review as it may be no longer be valid due to reduced usage resulting in low flow/water stagnation.

This risk assessment should review the potential for microbial growth during the shutdown period and the measures that need to be taken to minimise the risk of infections as a result of biofilm formation within the pool, pipework and components.

Swimming pools themselves should be safe against microbiological hazards as long as they are chlorinated properly and operated to PWTAG standards.

Spa pool recommissioning process should be as follows.

Below are the steps which should be followed when recommissioning spa pools:

  1. Disinfect
    Water disinfection to reduce microbial growth, typically with 50mg/l chlorine for at least one hour, with the pH kept as near to 7.0 as possible during this period.
     
  2. Prove
    Evidence that safety standards have been met.
     
  3. Test
    A comprehensive functional water test to ensure the spa pool system operates correctly.
     
  4. Sample
    Chemical and bacteriological analysis of the water to ensure operating parameters are achievable and being maintained.
     
  5. Maintain
    You must then continue to adequately control Legionella within these systems.

The spa pool should be fully tested to confirm its functional safety and fitness for its intended purpose before being brought back into use, and the procedure and results should be fully documented.

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Last updated: 05/11/2020 12:30