While Legionella bacteria is a well-known health concern in water systems, it’s important to understand its relevance in fire sprinkler systems.
Legionella is a naturally occurring bacterium found in freshwater environments. Under certain conditions such as stagnant water, warm temperatures (20–45°C), and the presence of nutrients. It can multiply and pose a risk of Legionnaires’ disease, a serious form of pneumonia transmitted through inhalation of contaminated water droplets.
In short: not usually. Fire sprinkler systems are classified as low-risk when it comes to Legionella.
Closed Systems: Most sprinkler systems are sealed and contain stagnant water that is not regularly aerosolised, reducing the chance of airborne transmission.
Cold Water Storage: Sprinkler systems typically store water below the temperature range that promotes Legionella growth.
Infrequent Activation: These systems are only activated during fire emergencies or routine testing, limiting exposure opportunities.
Although rare, certain conditions can elevate the risk:
Wet Pipe Systems in Warm Environments: If water sits in pipes exposed to heat, it may reach temperatures conducive to bacterial growth.
Poor Maintenance: Lack of regular inspections or stagnant water in infrequently tested systems can increase risk.
System Modifications or Downtime: Changes to pipework or prolonged inactivity may introduce contamination.
We follow industry best practices to ensure your fire protection system remains safe and compliant:
Routine Flushing & Testing: Regular maintenance prevents stagnation and ensures water quality.
Cleaning Protocols: If systems are modified or temporarily decommissioned, proper cleaning and disinfection procedures should be completed before reactivation.
Legionella is a naturally occurring bacterium that can become a health risk when water is allowed to stagnate within man-made systems. In fire sprinkler systems, particularly those incorporating stored water tanks or sections of pipework with little movement, there is potential for water to sit for extended periods. While the primary purpose of a sprinkler system is fire protection, it is equally important to ensure that water hygiene is not overlooked. A well-designed and properly maintained system significantly reduces any risk, but responsible management remains essential.
Good practice begins with appropriate system design. Keeping pipe runs efficient, avoiding unnecessary dead legs, and ensuring adequate water turnover all help prevent stagnation. Where sprinkler systems rely on dedicated water storage tanks, these should be correctly specified, insulated where necessary, and fitted with secure, sealed lids to prevent contamination from debris, insects or vermin. Tanks should also be screened and protected from excessive heat, as warmer water temperatures can encourage bacterial growth. Regular inspection of tank condition, including checking for sediment build-up, corrosion or biofilm, is a key part of maintaining water quality.
Ongoing maintenance plays a vital role in reducing legionella risk in sprinkler systems. Periodic flushing, routine servicing and documented inspections help ensure that water remains clean and that the system continues to operate as intended. Property owners, landlords and duty holders have a legal responsibility to assess and manage Legionella risks within water systems under UK health and safety legislation. By combining effective fire protection measures with sensible water hygiene controls, building owners can ensure their sprinkler system remains both compliant and safe — protecting occupants not only from fire, but from avoidable water-borne health risks as well.
Visit the governments website for more information on water hygene in stored tanks.
All rights reserved. GFS Doncaster Limited
