Should you do your own legionella risk assessment or hire a professional?
On this page
Key points
- Either route is lawful. The duty is a suitable and sufficient assessment; who carries it out depends on competence, not on holding a particular qualification.
- DIY suits simple systems: a single dwelling, a combi boiler, no storage tanks, occupiers at ordinary risk.
- Professionals earn their fee on complex systems: tanks, calorifiers, long pipe runs, cooling towers, healthcare, and anywhere you cannot trace the pipework.
- The test is honesty about competence. If you cannot confidently answer what the system contains and where the risks are, you are not the competent person for it.
- Neither route certifies anything. An assessment identifies and evaluates risk; the duty to control and record continues afterwards.
You can do your own legionella risk assessment if you are competent to do it, and you should pay a professional when you are not. There is no legal requirement either way: ACOP L8 requires a suitable and sufficient assessment carried out by, or with the help of, competent people, and it is silent on whether those people are you or a contractor. The real question is not "am I allowed?" but "am I honestly able?"
This page is a decision aid. It sets the two routes side by side, gives you a way to judge which fits your building, and is blunt about where the DIY route runs out. Our page on doing your own assessment covers the DIY method itself; this one is about choosing.
The two routes compared
| Do it yourself | Commission a professional | |
|---|---|---|
| Legal standing | Fully acceptable if you are competent | Fully acceptable; competence is bought in |
| Best suited to | Single dwellings, combi boilers, small offices, simple systems you can walk and trace | Stored water tanks, calorifiers, plant rooms, long pipe runs, cooling towers, spa pools, healthcare and care settings |
| What you need | Time, access to every part of the system, and a structured template following L8 and HSG274 | A clear brief, and checks on the assessor's competence and what the report will contain |
| Cost | Your time only | A fee that scales with system size and complexity; the cost calculator gives an indicative figure |
| Weakness | You may not know what you do not know: dead legs, dead ends, poor calorifier circulation | Quality varies; a cheap tick-box report is worse than an honest DIY assessment |
| What it gives you | An assessment you understand because you did it, and records you can maintain | Independent eyes, system knowledge, and a written report you can show an insurer, agent, or inspector |
A decision aid: which route fits your building?
Work through these questions honestly. They are the same questions competence turns on.
- Can you describe the whole water system? Where water enters, whether anything is stored, how hot water is generated, and every outlet it feeds. If you do not know whether there is a tank in the loft or how the cylinder is heated, stop here: that gap is exactly what assessments exist to close.
- Is anything stored? Cold water storage tanks and calorifiers introduce the highest-risk components in most buildings. Once storage is involved, the assessment needs to judge condition, turnover, and circulation, which takes experience.
- Who uses the water? Ordinary occupants in a house or office are one thing; elderly residents, patients, or anyone immunosuppressed raise the stakes and the standard expected. Care and healthcare settings lean strongly towards professional input, as our care homes guide explains.
- Can you spot the classic faults? Dead legs, unused outlets, tank lids missing, tepid blended water held at growth temperature. If these terms are new to you, read what dead legs are and the temperature chart first; if they still feel like guesswork, buy the competence.
- Would your assessment survive being read by someone else? An insurer after a claim, an HSE inspector, a coroner's court. A suitable and sufficient assessment is written, specific, and reasoned. If yours would be a form with ticks, it is not sufficient, whoever filled it in.
Most landlords of ordinary domestic lets answer these comfortably and assess their own properties using our risk assessment builder. Most commercial buildings with plant rooms answer at least one question badly, and that is the professional's market.
Competence is not a certificate; it is whether you can honestly identify the risks in this particular system. If you cannot trace the pipework, you cannot assess it, and no template fixes that.
What a professional actually adds
A good assessor brings three things a template cannot. First, pattern recognition: they have seen hundreds of systems and spot the dead leg behind the boxing, the calorifier that never reaches temperature, the tank fed by a lukewarm supply. Second, independence: they have no interest in minimising the findings, which matters when the assessment is later scrutinised. Third, a structured written product: an asset register of outlets, photographs, reasoned risk ratings, and a written scheme of control, ideally drafted in line with BS 8580-1, the risk assessment standard.
What they do not bring is a guarantee. A professional report records what was found and recommended on the day. It does not certify the building as safe, and the duty to carry out and record the controls remains yours. Our page on the difference between LCA-registered and other assessors covers how to choose between providers.
Free legionella risk assessment template
A structured Word document following the five-step approach in ACOP L8. Covers risk identification, written scheme, monitoring, and records. If it isn't written down, you can't evidence it.
Follows ACoP L8 and HSG274 Part 2. Free. No spam.
The route that is never right
One option is off the table in both columns: nothing. Whether you do it yourself or commission it, the assessment must exist, be written down where there are five or more employees or the risk is not trivial, and be reviewed regularly, typically around every two years and sooner when the system or building use changes, as explained in how often to review an assessment. Whichever route you choose, the outputs land in the same place: identified risks, a written scheme, and a log book recording the controls, kept for at least five years. The choice is only ever about who does the thinking, never about whether it gets done.
Free legionella risk assessment template
A structured Word document following the five-step approach in ACOP L8. Covers risk identification, written scheme, monitoring, and records. If it isn't written down, you can't evidence it.
Follows ACoP L8 and HSG274 Part 2. Free. No spam.
Frequently asked questions
Can I do my own legionella risk assessment?
Yes. There is no legal requirement to hire a consultant, and ACOP L8 accepts that a duty holder can carry out their own assessment provided they are competent, meaning they understand their water system, know the guidance, and can identify and evaluate the risks. For a simple domestic rental property with a combi boiler, a careful landlord using a structured template can usually do this themselves. For complex systems with tanks, calorifiers, or vulnerable occupants, professional help is the sensible call.
When do I need a professional legionella risk assessment?
Commission a professional when the system is beyond what you can honestly assess: stored cold water tanks, calorifiers and plant rooms, long or complex pipe runs, cooling towers or spa pools, healthcare or care settings with vulnerable occupants, or any building where you cannot trace the pipework yourself. Also consider one after a positive sample, a prosecution or improvement notice, or when an insurer, lender, or managing agent expects an independent report.
How much does a professional legionella risk assessment cost?
Cost depends mainly on the size and complexity of the water system, the number of outlets and tanks, and the time on site, so a small flat costs a fraction of a hotel or office block. Our legionella risk assessment cost calculator gives an indicative figure for your type of premises. Whatever the quote, check what it includes: the site visit, a written report, an asset register of outlets, and a written scheme of control are the pieces that matter.
Is a professional legionella risk assessment a legal requirement?
No. The legal duty is to have a suitable and sufficient risk assessment, not to have it done by any particular person or company. What matters is competence. A professional assessment is one way of achieving competence; a competent duty holder doing their own is another. Neither route certifies the building as safe: the assessment identifies and evaluates the risk, and the duty to control it continues afterwards either way.
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