Is a legionella risk assessment a legal requirement?

The legal duty is to assess and control the risk of exposure to legionella, which for most premises means carrying out a risk assessment. The HSE's Approved Code of Practice L8 sets out how to comply. The duty applies to employers, those in control of premises and landlords, and it exists whether or not the water system looks complicated.

How often should legionella temperature checks be done?

The risk assessment sets the schedule, but monthly temperature checks at sentinel outlets and weekly flushing of infrequently used outlets are common. Record temperatures as actual readings, not ticks, because a run of readings is what demonstrates the system is holding temperature.

Does a legionella risk assessment require water sampling?

Usually not. Control normally relies on keeping water outside the temperature range where the bacteria multiply and preventing stagnation, with monitoring to show that is happening. Sampling is used in specific circumstances, and the risk assessment should say whether yours is one of them.

Premises & property

Legionella risk assessment and water checks

Who has a duty to assess legionella risk, what a risk assessment covers, and the routine monitoring that follows from it.

This is a plain-English explainer, not legal advice. The authority on this topic is the Health and Safety Executive. Rules change — check the current official guidance before relying on it.

Anyone responsible for premises has a duty to assess and control the risk of exposure to legionella bacteria in water systems. The duty applies to employers, those in control of premises, and landlords, and it's set out in health and safety law with the detail in the HSE's Approved Code of Practice, L8.

The common misconception is that this means testing the water. Usually it does not. It means assessing the risk, and then controlling it: most often by keeping water either hot enough or cold enough, and preventing stagnation.

What a risk assessment covers

The water systems

How water is stored, heated and distributed.

Conditions for growth

Principally temperatures between roughly 20°C and 45°C.

Where water stagnates

Infrequently used outlets, dead legs, unused rooms.

Who could be exposed

And whether anyone is more vulnerable.

The controls in place

And how their effectiveness is checked.

The assessment is reviewed periodically, and whenever the system or its use changes.

The routine that follows

The assessment produces the schedule, and this is where it becomes an operational matter instead of a document:

Temperature checks

At sentinel outlets, recorded as readings rather than ticks.

Monthly

Flush unused outlets

The ones nobody would otherwise think about.

Commonly weekly

Inspect tanks and calorifiers

Interval set by the risk assessment.

Periodic

Records of all of it

The part that proves the rest happened.

Kept and reviewable

Both parts matter. A risk assessment with no monitoring behind it's a document describing a system nobody checks.

Why the records are the hard part

The assessment is the easy half

It happens once and is usually done well, often by a contractor. The weekly flushing and monthly temperatures are internal, unglamorous and easy to skip, and they are the part that demonstrates ongoing control.

Recording a temperature as a number rather than a tick is what makes the record useful: a run of readings shows whether the system is actually holding temperature, which a column of ticks can't.

Common questions

Is a legionella risk assessment a legal requirement?: The legal duty is to assess and control the risk of exposure to legionella, which for most premises means carrying out a risk assessment. The HSE's Approved Code of Practice L8 sets out how to comply. The duty applies to employers, those in control of premises and landlords, and it exists whether or not the water system looks complicated.
How often should legionella temperature checks be done?: The risk assessment sets the schedule, but monthly temperature checks at sentinel outlets and weekly flushing of infrequently used outlets are common. Record temperatures as actual readings, not ticks, because a run of readings is what demonstrates the system is holding temperature.
Does a legionella risk assessment require water sampling?: Usually not. Control normally relies on keeping water outside the temperature range where the bacteria multiply and preventing stagnation, with monitoring to show that is happening. Sampling is used in specific circumstances, and the risk assessment should say whether yours is one of them.

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