WATER TREATMENT
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monitoring tools are being deployed, however calibrated they may be. Infrared thermometers typically used for surface readings cannot read accurately through thick metallic cylinder or cistern walls. The result is a reading that’s potentially misaligned with the water’s true temperature. It’s an error that direct access to the water doesn’t automatically solve itself. Many operators will take internal water temperature readings using one single probe at a fixed point. In doing so, they overlook the internal stratification that easily occurs through poor mixing, insufficient tank turnover and cold-water ingress points. Using routine spot checks as the primary monitoring touchpoint can result in none of these failures getting caught in time. While water temperature may appear within safety parameters on inspection day, it may have been cycling in and out of the Legionella danger zone for weeks beforehand. Without equipment that reports both accurately and continually, operators are relying on pure chance to identify risks.
Beyond box ticking: the case for smarter Legionella monitoring
Jason Webb, managing director of Electronic Temperature Instuments (ETI) makes the case for precise temperature monitoring in Legionella prevention and explains the active role installation firms can play
T
he Health and Safety Executive’s (HSE) guidance around Legionnaires’ disease prevention is highly specific on the
temperature thresholds to avoid within stored, distributed and outlet water. As the waterborne bacteria only becomes hazardous when allowed to multiply between 20ºC and 45ºC, cold water should be kept below 20ºC and hot water at 60ºC or higher. The latter should never go below 50ºC when distributed, with a 55ºC safety threshold recommended for healthcare settings. What the guidance is far less specific about is how
that compliance should be monitored and maintained in practice. It allows building managers to default to compliance-driven box-ticking – monthly spot checks treated as proof that stored water is free from bacterial risk. As a result, they remain unaware of how the water within a calorifier or storage cistern behaves on a daily basis. When inaccurate monitoring equipment is used simultaneously, it becomes a recipe for legal, financial and reputational disaster that can easily implicate the suppliers and installers involved. This is where installation firms can play a
proactive role in Legionella control. By developing 26 August 2026
Left: Jason Webb, managing director of Electronic Temperature Instuments (ETI
an understanding of poor monitoring strategies, and recommending the precise, real-time and traceable equipment needed to fix them, routine service calls can be turned into something far more valuable.
Identifying poor monitoring practice
Infrequent calibration is the first source of inaccuracy installers should be aware of. When probes and sensors aren’t regularly recalibrated or replaced to uphold performance, this creates a ‘calibration gap’ between actual water temperature and what’s being reported. It’s also important to recognise when unsuitable
Offering the solutions
Recommending regular and well-documented calibration provides clients with a simple starting point. Probes and sensors should be calibrated annually as a minimum benchmark, with equipment certified by bodies like the United Kingdom Accreditation Service. This should be even more frequent for critical settings such as healthcare – a sector that warrants its own compliance threshold within the HSE’s official guidance. Suggesting immersion probes over infrared surface thermometers, multiple-point monitoring within a tank and sufficient stabilisation time will improve spot- check accuracy further. Specifying smart and connected monitoring devices is another wise move. Bluetooth-enabled thermometers automatically log temperature readings at the start and end of a test, confirming whether running water complies with legal requirements – falling below 20ºC within two minutes, or rising above 50ºC within one. Many also offer the ability to upload results directly to a digital archive, creating a compliance record that can be relied upon during HSE inspections. But accurate record-keeping should always be part of a wider integrated monitoring approach, which can be achieved by feeding Bluetooth-logged data into Building Management Systems (BMS). By flagging anomalies in trend data and triggering remedial actions, these platforms increase visibility while reducing the need for cumbersome manual intervention. For FMs overseeing multiple sites, ageing infrastructure and stretched teams, it’s a transformative shift that’s also likely to be cost- effective – many sites will already be using a BMS for other FM functions. For installation teams, it’s yet another example
of how they can add value far beyond their remit. As Legionella control comes under greater scrutiny in the built environment, the installers who can speak confidently about precise, real-time and traceable monitoring technology will be the ones building managers remember – and call again.
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