Legionella is the single most searched water hygiene topic among property managers, and for good reason. A poorly managed water system can create the conditions for Legionella bacteria to grow, putting residents, staff and visitors at risk, and exposing building owners to serious legal and financial consequences. Yet despite its importance, Legionella control is often treated as an afterthought, bolted onto general water treatment rather than managed as the standalone compliance obligation it actually is.
At Balance Mechanical, we see water hygiene as a discipline in its own right, sitting alongside heating, ventilation and drainage design rather than beneath it. Here is what property managers, building owners and facilities teams need to understand.
Understanding your Legionella risk assessment obligations as a property manager
Under the Health and Safety at Work etc. Act 1974 and the Control of Substances Hazardous to Health Regulations (COSHH), anyone in control of a premises has a legal duty to assess and manage the risk of exposure to Legionella bacteria. This duty applies to landlords, property managers, employers and anyone responsible for a water system, regardless of the size or type of building.
A Legionella risk assessment should identify every part of the water system where bacteria could grow and where people could be exposed to contaminated water droplets. This includes hot and cold water storage tanks, calorifiers, pipework, showers, taps, cooling towers and any little-used outlets. The assessment needs to be carried out by someone competent to do so, and it needs to be reviewed regularly, particularly whenever the water system changes or if there is reason to believe the original assessment is no longer valid.
Many property managers assume a risk assessment is a one-off document to file away. In reality, it is a living record that should evolve alongside the building, its occupancy, and its water system.
Legionella control in hot and cold water systems: what building owners must do
Legionella bacteria thrive in water between roughly 20 and 45 degrees Celsius, which means both hot and cold water systems need active management to stay outside that danger zone.
For hot water systems, this typically means storing water at 60 degrees Celsius or above and ensuring it reaches at least 50 degrees Celsius within one minute at the outlet. For cold water systems, the aim is to keep water below 20 degrees Celsius, which requires attention to pipe routing, insulation and proximity to heat sources.
Beyond temperature control, building owners need to think about system design more broadly. Dead legs, redundant pipework and infrequently used outlets are all classic sites for stagnant water and bacterial growth. Water storage tanks should be sized appropriately for demand, fitted with tight covers to prevent contamination, and kept clean. Where a building has been vacant, or parts of a system have not been used for an extended period, a flushing regime is essential before normal use resumes.
None of this is a one-off fix. Legionella control is an ongoing responsibility that needs to be built into how a building is operated day to day, not just addressed at handover.
How often should water hygiene checks be carried out in a residential block?
There is no single answer that applies to every building, since the correct frequency depends on the system, its complexity and the outcome of the risk assessment. That said, there are some widely recognised baseline intervals for residential blocks.
Monthly checks typically include recording temperatures at sentinel taps, both nearest to and furthest from the calorifier or hot water source, alongside a visual inspection for any obvious issues.
Quarterly checks often extend to a wider sample of outlets, along with checks of shower heads and hoses for signs of scale or biofilm.
Annual checks usually involve a full review of the risk assessment, tank inspections, and more detailed system checks, including cold water storage tank conditions and calorifier temperatures.
Where a system includes higher-risk features, such as cooling towers or evaporative condensers, checks may need to be considerably more frequent, and formal notification to the local authority may also be required.
The right schedule for any given block should be set out clearly in the risk assessment itself, with responsibilities assigned and records kept as evidence of compliance.
L8 ACOP compliance: a plain-English guide for facilities managers
The Approved Code of Practice L8, commonly referred to as ACOP L8, sets out how duty holders should comply with the legal requirement to control Legionella risk. Alongside it sits HSG274, a set of more detailed technical guidance covering different types of water systems.
In plain terms, L8 compliance means being able to demonstrate that you have:
- Identified a responsible person to manage Legionella risk
- Carried out and documented a suitable risk assessment
- Put a written control scheme in place, setting out how risk is managed day to day
- Implemented that control scheme through monitoring, maintenance and record keeping
- Reviewed the risk assessment regularly and whenever circumstances change
For facilities managers juggling multiple sites, the practical challenge is usually not understanding what L8 requires in principle, but keeping the paperwork, monitoring and maintenance in step across every building under their control. A missed monthly temperature check or an out-of-date risk assessment can be enough to leave a duty holder exposed, even where day-to-day water management is otherwise sound.
Working with a specialist who understands both the mechanical systems involved and the compliance framework around them takes a significant burden off facilities teams, and reduces the risk of gaps appearing between design intent and operational reality.
Why Legionella control belongs in the mechanical conversation
Legionella risk cannot be separated from the mechanical design of a building. Pipe layout, water storage, temperature control and system balancing all directly affect how easily bacteria can establish themselves. A water treatment regime is only as effective as the system it is protecting, and a system designed without water hygiene in mind will always be harder and more expensive to manage safely.
At Balance Mechanical, we design and maintain water systems with Legionella control built in from the outset, not added as an afterthought. From risk assessment through to ongoing monitoring and maintenance, we help property managers and facilities teams stay compliant, protect building occupants, and avoid the costly consequences of getting water hygiene wrong.
Our team would be happy to discuss your building’s water hygiene compliance and help you put a robust, practical control scheme in place. Call us on 01483 378033 or email info@balmech.co.uk to get in touch.
