Seasonal Risks

by Adam Lewis, on 18-12-2019



As we move into the festive season, we look at what effect this may have on the control of legionella in domestic water systems and the associated risks.

Holiday Mode

As we wind down and prepare for Christmas our minds can be elsewhere, on parties, presents and preparations. Normal work duties are sometimes relaxed and often disregarded as something for the New Year. Without due care and attention there is a risk that important activities, which manage and control the risk of legionella, may be missed or delayed. It is everyone’s duty to ensure the health and safety of each other and complacency should be avoided.


Business and School Shutdown

Many businesses and organisations such as schools and manufacturers have shutdown periods during the holidays. This can leave water systems vulnerable to an increased likelihood of bacterial colonisation due to infrequent use and storing water for longer than is acceptable. It is important to review and adapt control measures to the atypical operating conditions in these buildings and ensure that water systems remain under control and safe for use on return to normal operation.


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Increased Susceptibility

This time of year, we see an increase in ill health, particularly in the elderly. While their defences are compromised its reasonable to assume that the likelihood of legionella infections and developing complications may be increased. Care should be taken to consider the susceptibility of the building population when undertaking and reviewing risk assessments and control measures along with the effect this increased susceptibility may have on risk.


Turning up the Heat

As the heating gets turned up so does the risk of heat transfer to cold water distribution systems. Hot plant rooms can also increase the temperature of stored water if the tanks are located nearby. Particular attention should be given to cold distribution systems to ensure that thermal gain is kept to a minimum. It is also important to ensure that hot and cold pipework is tracked and sufficiently insulated to ensure that the rate of heat transfer is minimised.


Holiday Cover

At this time of year lots of holidays are taken leaving the systems vulnerable if appropriate cover is not in place while key players in the management of legionella take their leave. It is important to ensure that suitable cover is in place for key duties to maintain control and ensure continuity of the scheme.


Hot Tubs and Spa Pools

Spas pools and hot tubs are a great way to get out of the cold weather. As we know, however, spa pools and hot tubs represent a significant risk of legionella colonisation & human exposure, if not managed correctly. Due to this risk, it is essential that these systems are operated and maintained in accordance with good practice guidance, such as the Health & Safety Executive’s [HSE] HSG282 “Control of legionella and other infectious agents in spa-pool systems” and the Pool Water Treatment Advisory Group’s [PWTAG] “Hot Tubs for Business”.


Seasonal and Temporary Staff

During this time of year, particularly in hospitals and healthcare premises, lots of additional staff can be recruited without familiarity and knowledge of the premises, its systems and how they operate. This could present an increased risk, particularly if untrained staff are conscripted to undertake maintenance tasks or unfamiliar staff adjust or change systems without knowing what effect this may have on the control of the system. It is important to communicate awareness of legionella risks and the associated control measures to new staff.


Reduced Incoming supply and Cold Temperatures

As the cold weather sets in and the cold water supply temperatures drop this may affect the operating temperature and recovery time of some water heaters. Care should be taken to ensure hot water storage and distribution temperatures remain compliant during cold periods – be prepared to make adjustments.


Frozen Assets

Cold weather also brings the risk of freezing to external assets and those in unheated spaces. In turn damage or complications may be caused that compromise the effectiveness of legionella controls measures. For example, frozen water in the trap of an air-handling unit can prevent the free drainage of waste water causing a build-up in the unit’s drip tray. The pooling water may be distributed throughout the system and dispersed into the building. It is essential to assess the vulnerability of external systems and those located in unheated spaces to ensure they are not exposed to the risk of freezing.


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.


From everyone here at the Water Hygiene Centre, we would like to wish you a very merry Christmas and a Happy New Year.


Editors Note: The information provided in this blog is correct at date of original publication - December 2019.

© Water Hygiene Centre 2019


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About the author

Adam Lewis

Adam is an experienced risk assessor with an extensive portfolio of risk assessments in many industries and sectors including Ministry of Defence and local and central government with a view to specialise in hospitals and healthcare premises, covering the whole of the United Kingdom.

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