Designing a Compliant Legionella Monitoring System

Everything starts with the schematic

Before you think about visits, sensors, data, or cost, there is one non-negotiable requirement:

You need an accurate schematic drawing of your water system.

If your schematic is wrong, everything built on top of it is compromised. Monitoring points are guessed rather than justified. Data; whether manual or automated becomes misleading. And when something goes wrong, explaining why decisions were made becomes extremely difficult.

This is true whether you:

• continue with traditional manual temperature checks, or
• move toward automated monitoring

An accurate schematic is what connects the physical system, the risk assessment, and the monitoring regime into something defensible.

If your schematic isn’t right, you can prove activity, but not control.

If you need help correcting or producing a compliant schematic, we provide this as a standalone service.

Where legislation expects you to demonstrate control

UK guidance (ACoP L8 and HSG 274 Part 2) doesn’t expect you to “check a few outlets and hope for the best”.

It sets clear expectations about where control must be demonstrated.

Using the schematic example in Appendix 4 of HSG 274 Part 2, this walkthrough shows you how to identify monitoring requirements across your system — including:

This stage isn’t about technology.
It’s about understanding how many points of visibility are actually required to demonstrate control of your system.

Once you see this mapped properly, compliance stops feeling vague.

Turning a schematic into a monitoring strategy

When your schematic is accurate and legislative expectations are clear, the next step becomes straightforward.

Healthcare & NHS

• Wards closed and services suspended
• Patients and staff relocated
• £1m+ impact to mental health services
• £46m facility opening delayed

Care & Housing

• Care home evacuations
• Sheltered housing fines (£900k)
• Multiple housing schemes affected

Leisure & Community

• Repeat closures
• Permanent closure and £1.5m demolition
• £3m repair costs

Education

• 600 pupils unable to start term
• Emergency closures and isolated water supplies
• Special schools shut at short notice

Justice & Civic Buildings

• Prisoner death and legal consequences
• Council HQ closed immediately
• Legal buildings unable to reopen

How a “manageable issue” becomes a disruptive event

You rarely go straight from “everything is fine” to a full closure.

The pattern is usually a progression and the earlier you can see it, the more options you have.

What compliance gives you — and what it can’t

If you follow ACoP L8 and HSG 274, you’re doing what the system expects: you’re meeting a defined baseline and documenting evidence. That matters, but it also has limits.

Compliance gives you:

• Evidence that checks were completed
• Records for audit and governance
• Defined responsibilities
• A defensible baseline position

Compliance can’t give you:

• Continuous visibility of system behaviour
• Early warning of deterioration
• Insight between inspection points

This is not a failure of people or process. It’s a limitation of periodic oversight in systems that change continuously.

The cost of late discovery

If you’re accountable for risk, the question is rarely “can we pass an audit?”
It’s “what happens if we’re forced into disruption?”

If you manage multiple sites, you carry a different kind of risk

As the number of sites you oversee grows, so does the likelihood that Legionella will develop somewhere, even if controls are in place.

Not because you’re careless.

Because checks are periodic and systems evolve between them.

At scale, the biggest exposure is often not illness.

It’s the operational and reputational impact when deterioration is discovered late and forces immediate action.

A reality check

As you look through the examples on this page, you’ll already know which sites concern you most.

Not hypothetically but specifically.

The buildings where systems are complex.

The facilities with vulnerable occupants.

The sites where closure would be hardest to explain.

This page isn’t asking you to act immediately.

It’s asking you to pause and consider one question:

If conditions began deteriorating quietly in one of your buildings, how early would you know and how disruptive would discovery be when it finally came to light?

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Talk it through before disruption forces the conversation

If you want to discuss what earlier visibility could look like across your sites and how it reduces disruption risk we’re happy to help.

Our team is ready to help whether you manage one site or many.

or call 01827 259346 to get started today.