Legionella Management and Control in Summer

by Water Hygiene Centre, on 21-07-2017
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Summer has arrived here in the UK! With average summer temperatures of around 22°C - 30°C. Cases of Legionnaires’ disease are known to increase during summer months. This is in part due to increased ambient temperatures that encourage bacterial proliferation in water systems if the right conditions are present.

Legionella Guidance

The UK has some of the most robust guidance regarding Legionnaires’ disease, but there is a lack of information regarding how to approach the issue of increased water temperatures in summer months. The guidance is based, for the most part, on a continuous control programme albeit one that ought to react appropriately to failures or other indicators of poor performance.


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Legionella Issues in Summer

Legionella bacteria begin to multiply at temperatures above 20°C and with some regions of the UK receiving mains cold water in excess of 25°C during the height of the summer this can be considered a foreseeable risk factor. The Water Supply (Water Quality) Regulations however states that water can be supplied at up to 25°C to a premises which conflicts with HSG274 and HTM04-01 guidance on water temperature for the control of legionella.

In these cases those persons responsible for water safety should revise their Legionella risk assessment and control measures to remain compliant, however when incoming water temperatures exceed 25°C then the water company should be notified, who must investigate and remedy the high water temperature.


In 2017 a man from Norfolk died due to inhaling legionella bacteria emanating from a hosepipe containing stagnant water was well documented in the national press.


Legionella risk for schools in summerThere is also an increased legionella risk in the summer months in buildings that remain vacant for long periods of time such as schools, colleges and universities. It’s important that monitoring and maintenance tasks are kept up to date during long periods of little or no use and that cover should be in place for the absence of personnel involved in the management, operation and maintenance of water systems. Individuals assigned to cover these responsibilities should be familiar with the water systems and the control procedures and be competent to carry them out.


The increased use of air cooling systems during summer months can also be concern. In particular the use of portable evaporative air coolers, that don’t get used for much of the year and are not properly maintained can create problems. Evaprotive coolers were identified by NHS Estates in 1996 [Safety Notice NHSE SN(96)06 – ‘Evaporative type cooling fan] as a device that shouldn’t be used in healthcare facilities unless approved by the Infection Prevention Control [IPC] Team with strict control maintenance procedures in place. In HTM04-01 Part B it details the use of such devices rests with IPC Team. Are these devices in use within your healthcare facility and they are not known?


What can you do to Prevent Legionella Outbreaks During Summer Months?

Whilst we cannot directly influence the temperature of the water supplied to our premises by the water supply company, there’s a lot we can do to mitigate the risk of bacterial proliferation once the water has entered our buildings.


Water Safety Plan2-white-bgThe Water Safety Plan should be updated to reflect the increased risk during times of high ambient temperature. Increasing the frequency of flushing for little used outlets and more widespread temperature monitoring should be considered alongside a Legionella sampling regime. It’s also important to check cold water storage tank temperatures more regularly during periods of high temperatures [at least annually].


When considering healthcare settings and the increased risk associated with these sites due to the highly susceptible population, further measures may be needed. If site wide cold water temperatures are consistently high and/or sampling results suggest bacterial growth, then further engineering solutions should be developed. Examples include:


  • Minimising water age through the correct sizing of pipework & storage systems and/or removal of unnecessary storage;

  • Where possible, cold water pipework situated in close proximity to sources of heat (e.g. hot water pipework, radiators, warm plant rooms, steam pipework etc.) should be re-located;

  • Thermal insulation of pipework and storage tanks should be checked and upgraded as required.

More radical options such as refrigeration or biocidal treatments may also be considered as part of the solution! Although such options should be taken into consideration by the Water Safety Group [WSG].

If you have questions regarding the issues raised above or you would like to speak with one of our consultants please click here to get in touch.

 Editor’s Note: The information provided in this blog is correct at the date of original publication – July 2019

© Water Hygiene Centre 2019

Image by loredan from Pixabay 

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About the author

Water Hygiene Centre

The Water Hygiene Centre was established in 2009 to address the lack of independent water hygiene consultancy within the industry. From our humble beginnings, we have established ourselves as a market leader, helping clients identify and minimise the risk of waterborne contamination and disease, whilst improving compliance performance.

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