Legionella compliance is the legal duty to assess and control the risk of Legionella bacteria growing in building water systems. Legionella bacteria cause Legionnaires' disease, a serious form of pneumonia spread by inhaling contaminated water droplets from showers, taps, or cooling towers. Run across a multi-site portfolio, it's less a one-off pass and more a system you need in place day to day, which is where a platform like Joblogic fits in.

Where this guide picks up

A legionella risk assessment tells you where the risk sits and who is legally responsible for it. This guide picks up from there: the written scheme, the day-to-day monitoring schedule, the logbook, what to do when a reading falls outside the limits, and how to hold all of that together across multiple sites and contractors.

One line on duty holders: whoever is named as the duty holder in your risk assessment carries that legal responsibility throughout, whatever day-to-day tasks are delegated to a responsible person or an external contractor.

The written scheme of control: what it adds once the assessment exists

The risk assessment tells you where the risk is and how big it is. The written scheme turns that into daily practice: the exact monitoring tasks, who carries out each one, how often, and what happens when a result falls outside the limits the assessment set.

ACoP L8 requires a written scheme for any system where a risk has been identified. It needs a named responsible person, appointed by the duty holder and competent to manage it, plus named cover for when they're away. Tasks are easiest to keep on track when they're tied to a specific asset rather than a general to-do list: a tank, a calorifier, or a named outlet, not just "check the water system."

What separates a working scheme from a document that sits in a drawer is whether every task inside it is actually scheduled, assigned to an asset, and checked off, not just written down once at the start.

The monitoring schedule

These are the frequencies set out in HSG274, Part 2, Tables 1 and 2, the technical guidance supporting ACoP L8, with planned maintenance scheduling built around them. Treat them as a floor: if your own risk assessment calls for anything tighter, follow that instead.

Worth stating plainly: the weekly flushing of little-used outlets and the quarterly descaling of shower heads cover different things. Keep them as separate line items in the schedule so one doesn't get tracked as the other.

The logbook: what to record and where to keep it

The logbook is the evidence layer underneath the written scheme. It's what an HSE inspector asks to see. Per HSE's own guidance, it needs to show:

• Who's responsible for managing and implementing the written scheme
• The significant findings of the risk assessment
• The written scheme itself, and evidence it's being followed
• Whether each part of the system is currently in use or not in use
• Every monitoring, inspection, test, or check result, with the date

Retention is a two-tier rule, not a flat five years as it's often simplified to. General scheme and significant-findings records are kept for as long as they remain current, plus at least two years after they're superseded. Records of monitoring inspections, tests, and checks specifically are kept for at least five years. If your business has fewer than five employees, written records aren't a strict legal requirement, though HSE recommends keeping them anyway.

One extra duty worth including here since it trips people up: if you have a cooling tower or evaporative condenser on site, you must notify your local authority in writing under the Notification of Cooling Towers and Evaporative Condensers Regulations 1992, and tell them again if it goes out of use.

Keeping all of that in one system, rather than a mix of paper logs, emails, and a contractor's own spreadsheet, is what makes compliance records something you can hand over at short notice instead of assembling from scratch.

What to do when a reading falls outside the limits

A failed reading is the point the written scheme actually gets tested, not a sign it's failed. The sequence that needs to happen, and be logged, is:

1. Take the outlet or asset out of use if there's an immediate risk, don't let it run as normal.
2. Record the result, the date, and who found it.
3. Investigate the likely cause: scale, a dead leg, a failed TMV, or a broken recirculation pump.
4. Carry out the remedial action: flush, descale, repair, or disinfect, as the situation calls for.
5. Re-test before the outlet goes back into normal use.
6. Log the whole chain, not just the failure and the fix.

If the same fault keeps recurring at the same point, that's a signal to revisit the risk assessment itself, rather than keep logging the same remedial action.

Proving compliance across multiple sites

When you manage legionella compliance across multiple sites, the process is rarely the problem. The difficulty is making sure every site follows the same process, every check happens on time, and every record is captured correctly.

Common failure points in multi-site operations:

• Flushing and descaling schedules slipping because there's no site-level reminder in place.
• Evidence logged against the job rather than the specific asset record, so an auditor can't trace it back.
• Records split across paper logs, emails, and separate spreadsheets, making audit prep slow under pressure.

For contractors running planned preventative maintenance (PPM) contracts, this is where the pressure concentrates. A contract commits you to defined visit frequencies and evidence standards across every site. When mobilisation is rushed or asset lists are incomplete, schedules slip and records end up attached to the wrong asset, which creates exactly the audit gap an HSE inspection exposes.

Managing contractors and subcontractors on water hygiene

Most organisations don't run legionella monitoring entirely in-house. Calorifier inspections, TMV work, and bacterial sampling are often contracted out to a water hygiene specialist. That doesn't move the legal duty. The duty holder stays responsible for the outcome even when a subcontractor carries out the task, so a documented agreement about exactly who does what, at what frequency, matters as much as the work itself.

A few things worth getting right before a subcontractor starts:

• Scope and frequency in the contract should match your written scheme exactly, not a generic service schedule the contractor applies everywhere.
• Evidence standard: agree upfront what gets logged, in what format, and how quickly it reaches your records after each visit.
• Competence: check training and qualifications before appointing, and keep that evidence on file alongside everything else.

The usual failure mode with multiple subcontractors across a portfolio is fragmentation: one contractor's reports sit in their own system, another's arrive as emailed PDFs, and nobody can see the full picture without chasing three different inboxes.

How Joblogic supports it

The written scheme becomes something you can run, rather than a document that sits in a drawer, when the schedule, the logbook, and the people doing the work are in one system. Joblogic's planned maintenance module holds the task-by-task schedule at asset level, so flushing, descaling, and inspection tasks are tied to a specific tank, outlet, or calorifier rather than a generic job. Mobile forms can be set to mandatory, so a compliance form has to be completed before the job can even start, which stops engineers turning up without the right check already logged. Where water hygiene work is subcontracted, the subcontractor portal keeps compliance documents, qualifications, and job assignment in the same system as the rest of your operation, rather than in a separate inbox. A portfolio view that flags which site has a written scheme task overdue catches a logbook gap before an inspection does, not after.

Keeping the system current

ACoP L8 and HSG274 aren't static. HSG274 Part 1 was revised in March 2024, and client requirements in sectors like healthcare, social housing, and education have tightened around evidence of competency and audit readiness.

None of that changes what makes a system hold up under scrutiny: a schedule that's followed on time, evidence captured at the point of the visit, and monitoring tasks built into your workflow rather than tracked separately. What that looks like in practice depends on your own estate. A single site with a straightforward hot and cold water system needs far less than a portfolio with cooling towers and several water hygiene subcontractors, so it's worth checking your current setup against your own risk profile rather than a generic checklist.

If you want to see how Joblogic supports the written scheme and logbook side of legionella compliance specifically, book a demo and we'll walk you through it.

Frequently asked questions

How long do I need to keep legionella monitoring records?

ACoP L8 sets two different retention periods. General written scheme and significant-findings records are kept for as long as they remain current, plus at least two years after they're superseded. Records of monitoring inspections, tests, and checks are kept for at least five years.

Do I still need a written scheme if a subcontractor handles water hygiene?

Yes. The duty holder keeps legal responsibility for legionella control even when a specialist contractor carries out the monitoring and maintenance tasks. A documented agreement covering scope, frequency, and evidence standards doesn't transfer that responsibility, it just defines who does the work.

What's the difference between a legionella logbook and a written scheme of control?

The written scheme is the control document: it sets out the tasks, frequencies, and responsibilities. The logbook is the evidence that those tasks are being carried out, with dates, results, and the names of the people who did them.

What must happen when a reading falls outside the control limits?

The outlet or asset should be taken out of normal use if there's an immediate risk, the result investigated, and remedial action carried out, whether that's flushing, descaling, repair, or disinfection. The system should be re-tested before it goes back into normal use, and the whole sequence logged.

Do I need to notify anyone if I have a cooling tower?

Yes. Under the Notification of Cooling Towers and Evaporative Condensers Regulations 1992, you must notify your local authority in writing if you have a cooling tower or evaporative condenser on site, and tell them again if it goes out of use.