Temperature Monitoring: One of the Most Valuable Legionella Controls You May Be Underusing
Reference: VE-WA-010
Temperature monitoring remains one of the most valuable and widely used control measures within a Legionella management programme. It is well understood, it generates a continuous record of system performance, and it can provide early warning when system performance starts to drift. It is also, in our experience, the area where the gap between what duty holders think they are doing and what they are actually doing is widest.
What HSG 274 actually requires
The headline numbers from HSG 274 Part 2 are well known: cold water should generally be below 20°C within two minutes at sentinel outlets; hot water should generally reach at least 50°C within one minute at the tap, with healthcare premises often applying 55°C in line with HTM 04-01 and local policy; and calorifier flow temperatures should be above 60°C with a return temperature above 50°C.
What is less well known is the frequency expectation. Sentinel outlets should be checked monthly. A representative sample of all other outlets should rotate through on an annual cycle. Calorifier and cold water storage tank temperatures should be logged monthly. Infrequently used outlets should be identified and managed through an appropriate flushing regime, removal where practicable, or other control measures defined in the written scheme.
Where regimes typically fall short
Three patterns come up repeatedly:
- Sentinel outlets that drift over time. A building gets refurbished, taps move, branches get re-routed, and nobody updates the sentinel schedule. Five years on, the team is monitoring outlets that are no longer the near and far points on each branch.
- Infrequently used outlets that are flushed by exception. The site team flushes when they remember; the contractor flushes when they're on site; nobody owns the schedule end to end and the records have gaps.
- Records that exist but aren't analysed. Monthly readings get logged into a folder and never reviewed. Without trending you cannot see the slow drift of a calorifier failing or a system slowly losing heat through poor insulation.
The cost of doing it properly
Surprisingly low. A digital temperature probe, a well-designed schedule, and the discipline to actually walk the route every month is the bulk of it. Where the cost climbs is in remote monitoring systems — IoT temperature sensors that log continuously and alert when a reading falls outside set thresholds. For larger or critical sites those are often justified; for many sites the manual approach, done properly, is more than enough.
How we can help
Vectair Environmental's monitoring services range from full manual regimes through to remote monitoring options where appropriate, tailored to the criticality of the site and the client's management arrangements. We start from your existing risk assessment and written scheme of control and design a regime that fits both the regulatory expectation and the practical reality of your team.
To talk through a monitoring regime that actually gets done, contact our team on 0118 981 7437 or at
