Legionella temperature monitoring

Temperature control is the primary defence in most water systems. It only works if someone is taking the readings, and taking them in the right places.

Why temperature does most of the work

Legionella multiplies between 20°C and 45°C. Almost everything else in a control scheme exists to keep water out of that band, or to stop it standing still long enough to get there. HSE describes temperature control as the most reliable method, and in a hot and cold water system it is the control a regulator looks at first.

What a sentinel outlet actually is

A sentinel outlet is not a special fitting. It is the outlet chosen to represent the extremes of the system: typically the one nearest the storage and the one furthest from it, for both hot and cold. If the extremes are in range, the outlets between them usually are too.

Choosing them is a judgement about the system rather than a formality, and it is one of the things a risk assessment should record. An assessment that does not tell you which outlets are your sentinels has not finished the job.

What to check, and how often

These are minimum frequencies. A system with a history of failing readings needs more of them, not the same.

Sentinel outlets, monthly – Hot and cold, at the nearest and furthest points of the system.

Calorifier, monthly – Storage temperature checked every month, flow and return where fitted.

Cold water tanks, six-monthly – Tank temperatures checked at least twice a year, with the lid and screens.

Representative outlets, on rotation – Other outlets sampled across the year so the whole system is covered.

The readings that count

A reading on its own means little without the time it was taken over.

50°C within one minute – Hot water at the outlet, rising to 55°C in healthcare premises.

60°C in storage – Hot water stored at 60°C or above.

Below 20°C cold – Cold water stored and distributed below 20°C.

Two minutes for cold – HSG274 Part 2 checks that cold outlets fall below 20°C within two minutes of running.

Records are part of the duty, not admin

Keeping and maintaining records is one of the duties HSE sets out, not a by-product of the others. Every inspection, every reading and every remedial action belongs in the log, with the date and the name of whoever took it.

The practical test is simple. If an inspector asked for twelve months of sentinel temperatures tomorrow, could you produce them? A monitoring regime that exists but is not recorded is, from a regulator’s point of view, a monitoring regime that does not exist.

Monitoring you can evidence.

We run temperature monitoring regimes and keep the records that go with them.

For any enquiries or questions please call: 01707 527 069