The risk of legionella bacteria being present in hot or cold-water systems has never been greater due to the Covid-19 pandemic.

Even though the Government did a U-turn in the summer and encouraged people to work from home, there was no evidence that businesses and organisations were in a rush to return to offices and workplaces, and with the current nationwide lockdown in effect, the advice has changed again to work from home if you can.

This means tens of thousands of buildings across the UK have stood empty since March when the first national lockdown was imposed.

It’s important that hot or cold-water systems in buildings are used regularly because if there has been little or no water flow, the risk of legionella bacteria getting into the systems increase dramatically.
Specific factors that cause Legionella to grow in these systems include:

  • Tepid water temperature: hot water systems, spas/swimming pools, and showers are responsible for the majority of legionella outbreaks. Warm water, between 77 F and 108 F, is the optimal temperature range for Legionella growth.
  • Lack of disinfection/infrequent use of fixtures: Shower heads and faucets are two fixtures where bacteria can thrive if they are not cleaned or maintained properly.
  • Complex plumbing designs: Dead legs (a length of pipe leading to an outlet that is rarely or never used) and other design complexities can cause water to stagnate and create low/poor flow.

The important thing to stress is that even in the current climate, the vast majority of legionella outbreaks are preventable, with water temperature control being key.

Guidance from the Health and Safety Executive is as follows:

  1.  Hot water storage cylinders should store water at 60°C or higher
  2. Hot water should be distributed at 50°C or higher (thermostatic mixer valves need to be fitted as close as possible to outlets, where a scald risk is identified).
  3. Cold water should be stored and distributed below 20°C.
  4. A competent person should routinely check, inspect, and clean the system, in accordance with the risk assessment.
  5. You must identify ‘sentinel’ outlets (furthest and closest to each tank or cylinder) for monthly checking of the distribution temperatures.
  6. You should also check the hot water storage cylinder temperatures every month and cold-water tank temperatures at least every six months.
  7. Stagnant water favours Legionella growth. To reduce the risk, you should remove dead legs/dead ends in pipework, flush out infrequently used outlets (including showerheads and taps) at least weekly and clean and de-scale shower heads and hoses at least quarterly.
  8. Cold-water storage tanks should be cleaned periodically, and water should be drained from hot water cylinders to check for debris or signs of corrosion.
  9. Water samples should be analysed for Legionella periodically to demonstrate that bacteria counts are acceptable.

If your building has been closed for long periods due to Covid-19, or another reason, and a return to the office is planned in the future, ensure you have a legionella risk assessment carried out in advance.

Use a company which is registered with the Legionella Control Association (LCA) and which has signed up to the LCA Code of Conduct. Eton Environmental Group is one of these companies.

We also have our own online legionella training course which help duty holders comply with their regulatory health and safety requirements. This can be booked for just £15 per person via our website or in bulk (further discounts can apply) by contacting us directly on 01325 366886.