A legionella risk assessment in 2026 typically costs £75–£200 for an ordinary house or flat, rising to £150–£300 for a larger home, an HMO, or anywhere with a cold water storage tank or a hot water cylinder to check. Small commercial premises run £195–£400, and complex sites — care homes, hotels, anywhere with a cooling tower — are priced individually from around £400 upward. That's the fee for a competent person to check the water system, measure a handful of temperatures, and produce a written record.
The legal position here is different from every other landlord-compliance guide in this series. A fire risk assessment doesn't apply at all to an ordinary single let with no shared common parts. Legionella isn't like that. The duty to assess and control the risk comes from general health and safety law, not a housing-specific order, and it reaches every landlord letting every kind of property — a whole house, a flat, a single room in a shared house. There's no size or tenancy-type exemption to hide behind.
What there is, though, is a genuinely useful escape from paying for one. HSE's own guidance is explicit that most landlords can assess the risk themselves and don't need to be professionally trained or accredited — a position I haven't seen stated as plainly for any other compliance duty on this site. I'm a building surveyor and energy assessor, not a legionella risk assessor, so I don't carry these out myself. What follows is 2026 pricing cross-checked against several UK water-hygiene compliance firms, what the law actually requires, and where I think paying for a professional assessment genuinely earns its fee.
The short answer
Figures below were checked on 7 September 2026 against several independent UK water-hygiene and compliance firms' published 2026 price guides, cross-referenced against each other. As with the rest of this series, London and the South East — Dom’s patch included — commonly run 20–30% above the national figures quoted here.
| Property / system | Typical cost (2026) | What's included |
|---|---|---|
| Simple flat or house (mains pressure, combi/unvented cylinder) | Free – £150 | HSE says most landlords can do this themselves; a paid version is a short site check and written record |
| Larger home, HMO, or one with a tank/calorifier | £150–£300 | Loft tank inspection, calorifier temperatures, outlet survey, written report |
| Small office or commercial unit | £195–£400 | Site survey, system schematic, written risk assessment and log book |
| Care home, hotel, block with plant or a cooling tower | £400–£2,000+ | Full system assessment, often with water sampling; individually quoted |
The first row is the one that doesn't appear anywhere else in this series. For a genuinely simple domestic system — mains-fed cold water, an instantaneous combi or unvented cylinder rather than an old-style tank — HSE's guidance for landlords says the assessment doesn't need a specialist at all. What you're paying £75–£150 for, in that case, is someone else's time and a professionally worded document, not a legal necessity.
What drives the price
Whether there's a cold water storage tank or calorifier. A header tank in the loft and an older-style hot water cylinder both need their own checks — lid condition, insulation, temperature at the tank and at the calorifier — that a modern mains-pressure combi system simply doesn't have. This is the single biggest reason two similar-looking houses get quoted differently.
Number of outlets and layout. More taps, showers and little-used outlets (an outside tap, a guest bathroom) mean more points to check and more time on site.
Occupancy type. An HMO with several unrelated households sharing risers or a communal water system is treated more carefully than a single-family let, partly because the consequences of getting it wrong are shared across more people.
Cooling towers and evaporative systems. Rare in ordinary housing but common in larger commercial and healthcare buildings, these trigger a materially more involved assessment and often laboratory water sampling at £50–£200 or more per sample — a cost that doesn't apply to almost any residential letting.
Region. London and the South East trend 20–30% above the national figures quoted here, in line with most trades in this series.
Do you actually need to pay for one?
The operative law is the Health and Safety at Work etc. Act 1974 and the Control of Substances Hazardous to Health Regulations 2002, with the Approved Code of Practice known as L8 (now in its fourth edition) setting out how to comply, backed by the more detailed technical guidance in HSG274. None of that is housing-specific legislation — it's the same framework that covers any workplace or premises with a water system, which is exactly why there's no small-let carve-out the way there is for fire safety.
What HSE's own landlord-facing guidance then says is that most landlords can assess the risk themselves and do not need to be professionally trained or accredited, provided the property is straightforward: mains-fed cold water, an instantaneous or combi water heater rather than a stored-water system, normal turnover of tenants, and no unusual features. A simple written check — is the cold water genuinely cold, is the hot water hot enough at the tap within a reasonable time, are there any outlets that go unused for weeks at a time — dated and kept on file, is a legitimate way to meet the duty for that kind of property.
Where I'd genuinely want a paid, competent assessment is anywhere with a cold water storage tank or a calorifier — common in the older housing stock I spend most of my time surveying, where a header tank sits in the loft and a hot water cylinder rather than a combi does the heating. Those systems create the still, warmed water conditions legionella actually needs, and correctly reading a tank's condition or a calorifier's temperature profile is a different task from checking a shower runs hot. HMOs and any building with shared risers sit in the same category, partly for the water system itself and partly because a competent third-party record is a stronger position to be in if a council or an insurer ever asks who assessed the risk and on what basis.
For most of the private rental sector in between — an ordinary modern flat with a combi boiler, no tank, no cylinder — paying £100–£150 for what HSE describes as a task you can do yourself isn't dishonest on the assessor's part, but it isn't necessary either. Do it yourself, keep a dated written record, and put the fee toward something the property actually needs.
Where the HMO Management Regulations add to this
For licensed HMOs, the Management of Houses in Multiple Occupation (England) Regulations 2006 add a separate, related duty: the manager must take reasonable measures to ensure the water supply and system are maintained in good, clean condition and don't present an undue risk to occupants' health. A legionella risk assessment is the standard way to evidence that duty is being met if a council's environmental health team ever asks — it isn't itself a named mandatory HMO licence document the way a fire risk assessment or an EICR is, but turning up with nothing written down, for a shared water system serving several unrelated households, is a materially weaker position than it would be for a single family let.
What I'd watch for in a quote
- Ask what system features you actually have before agreeing to a "full" assessment. If there's no cold water storage tank and no calorifier, question a quote priced as if there is one.
- A dated, property-specific written record with the temperatures actually measured, not a template certificate with your address dropped in — there's no such thing as a legally recognised "legionella certificate," whatever the marketing calls it.
- Clear separation between the assessment fee and any monitoring, sampling or remedial work being offered alongside it — water sampling in particular is rarely needed for an ordinary domestic system.
- A stated review point — roughly two years for a low-risk domestic property, annually for an HMO or a tank/calorifier system — not an open-ended one-off.
- For a tank or calorifier system, evidence the loft was actually visited and the tank inspected, not just a desk-based document built from a floor plan.
Questions I get asked
Do all landlords need a legionella risk assessment, even for one ordinary let? Yes. Unlike a fire risk assessment, there's no small-single-let exemption here — the duty comes from the Health and Safety at Work Act and COSHH, and it applies to anyone who lets a domestic property, including a single room in your own home. What changes with property type is how much the assessment involves, and whether it's sensible to pay someone to do it.
Can I do my own legionella risk assessment instead of paying someone? For a straightforward property — mains-fed cold water, a combi boiler or unvented cylinder rather than an old-style tank system, normal occupancy — HSE's own guidance says most landlords can assess the risk themselves and don't need to be professionally trained or accredited. A twenty-minute check of stored water temperatures, tank condition where one exists, and any little-used outlets, written down and dated, is a genuinely defensible record for that kind of property.
How often does it need to be reviewed? There's no fixed statutory interval. The common working assumption for a low-risk domestic property is roughly every two years, or sooner after a change of tenant, a change to the water system, or a period the property has stood empty. Higher-risk properties — HMOs, anywhere with a tank or calorifier — are usually reviewed annually as good practice.
What actually happens if a landlord ignores this duty? In practice, nobody routinely inspects a private landlord's legionella paperwork the way a council checks an EICR or gas certificate at HMO licensing. The real exposure is what happens after something goes wrong — a reported case traced to the property, or a council investigation following a complaint — at which point having nothing at all is a breach of the Health and Safety at Work Act and COSHH, enforceable by HSE, and a poor position to defend an insurance claim from.
Most of the properties I survey that genuinely warrant a paid legionella assessment — older houses with a loft tank and a hot water cylinder rather than a combi, or a house that's drifted into HMO territory without the owner quite planning it — are also the ones where that water system shows up as a line item in a wider survey. My Buy to Let Survey reviews the property against all 29 HHSRS hazard profiles alongside its physical condition, which is a useful early flag for whether you're looking at a simple mains system or a tank-fed one before you decide whether this is a DIY job or a phone call. It sits alongside the wider landlord compliance picture I cover in EICR cost, gas safety certificate cost and fire risk assessment cost. Call 07946 618203 or get in touch for a straight read on a property before you commit.
Small print. This guide is general information, not advice on a specific property, and it doesn’t replace a proper risk assessment carried out with reasonable care and a written quote for your own building. Prices were researched and correct to the best of my knowledge on 7 September 2026; costs move and vary by region and property. Always get at least three written quotes if you decide to pay for an assessment, and check what your system actually contains — tank, calorifier, cooling tower, or none of the above — before you do.