Legionella Risk Assessment Cost: What to Pay in 2026

A legionella risk assessment from a professional company typically costs between £75 and £300 for a standard residential property in the UK. Commercial properties and complex buildings cost more — usually £150 to £600 depending on size and water system complexity. But the cost can also be zero, because HSE confirms that most landlords can do the assessment themselves without hiring anyone.

Here is a breakdown of what you should expect to pay, what's included, and how to decide whether a professional assessment is worth it for your situation.

Professional assessment costs by property type

Figures indicative as of 2026, based on market observation — varies by provider and region.

Property type	Typical cost	Notes
Single residential flat (combi boiler)	£75–£120	Lowest-risk system — most water treatment companies have a fixed price for this
Single residential house with stored cylinder	£100–£150	Slightly more complex than combi — cylinder temperature checks, tank inspection if present
HMO (up to 6 beds)	£150–£250	More outlets, shared bathrooms, higher inspection time
HMO (7+ beds, complex conversion)	£200–£350	Additional time for systems with potential dead legs or unusual configurations
Small commercial (office, retail unit)	£150–£300	Varies by water system type and number of outlets
Medium commercial building	£300–£600	Larger tank systems, TMVs, multiple plant rooms
Care home, dental practice, school	£400–£1,000+	Higher-risk occupants or specialist water systems require more detailed assessment

Prices vary significantly by region (London typically 20–30% higher), by company (national water treatment firms vs local operators), and by what's included in the quote. Always check whether the quote covers the initial assessment only, or includes a written report, re-assessment after corrective works, or ongoing monitoring.

What a professional assessment should include

A compliant legionella risk assessment is not a brief site visit. Under ACoP L8 and HSG274, the assessment must cover:

1. A water system inventory — all sources, storage, generation, distribution, and outlets mapped and described
2. Hazard identification — temperature conditions, stagnation risks, dead legs, aerosol-generating outlets
3. People at risk — occupants identified, with higher-risk groups noted (elderly, immunocompromised)
4. Risk rating — each hazard rated for likelihood and severity
5. Recommended control measures — specific actions to address each identified hazard
6. A monitoring schedule — frequency and method for ongoing temperature checks and flushing
7. A named responsible person — who is accountable for implementing the scheme

If the professional assessment your quote covers does not include all of these, ask why. A brief one-page form from a gas engineer is not a compliant legionella risk assessment under ACoP L8 — regardless of what it's called.

Annual vs one-off costs

The cost above is for the initial risk assessment. Legionella compliance is ongoing, not a one-time purchase.

After the initial assessment, you still need to carry out and record:

• Monthly temperature monitoring at sentinel outlets
• Weekly flushing of any outlet unused for seven or more days
• Quarterly showerhead and flexible hose descaling
• Assessment review when anything changes (new tenants, system modifications, extended voids)

Most professional water treatment companies offer annual managed service contracts that include the initial assessment, periodic reviews, and monthly monitoring visits. These typically cost £200–£600 per year for a standard residential property. The monitoring obligation cannot be contracted away permanently — even on a managed service, you are responsible for what happens between visits.

See our legionella log book guide for guidance on what records to keep and how.

The free alternative: self-assessment

For most landlords with standard residential properties, the alternative to paying for a professional assessment is doing it yourself — and this is explicitly permitted.

HSE states: "In most cases, the actions landlords need to take are simple and straightforward so compliance does not need to be burdensome or costly. Most landlords can assess the risk themselves and do not need to be professionally trained or accredited."

Self-assessment is appropriate for properties with:

• A combi boiler (no stored hot water)
• A standard stored cylinder
• Direct mains cold water (no cold water storage tank)
• A single let or small HMO

Self-assessment is NOT appropriate for:

• Buildings with cooling towers or evaporative condensers
• Care homes, healthcare settings, or dental practices
• Large cold water storage tanks (300+ litres)
• Properties with vulnerable occupants
• Complex HMO conversions where pipework changes may have created dead legs you cannot trace

If your property fits the simple-system profile, the main cost of self-assessment is your time — typically 30–90 minutes for the initial documentation, plus 15–30 minutes per month for temperature checks and flushing records.

LegioLog's Legionella Risk Assessment Template Generator creates a building-type-specific template document that covers all seven sections required under ACoP L8. It does not replace a professional assessment for complex systems — but for a standard let, it gives you a structured document to fill in.

Why some "legionella certificates" cost £150–£300

If you have seen services marketed as "legionella certificates" at these price points, be aware: there is no official legionella certificate in UK law. What these companies provide is typically a risk assessment plus a summary letter.

Our guide on what a legionella certificate actually is explains what you legally need versus what companies sometimes sell as a certificate.

Practical takeaway

For a standard single let or small HMO with a combi boiler or simple stored-cylinder system:

• Professional assessment: £75–£150, valid for up to two years (review sooner if anything changes)
• Self-assessment: your time — document with a structured template, record ongoing checks
• Annual managed service (assessment + monitoring): £200–£400 per year

For a complex system, care home, or high-risk building, a professional assessment is the practical standard — not because the law mandates it, but because the technical knowledge required genuinely exceeds what a non-specialist can reliably cover.

Before you commission a professional assessment, check that the quote explicitly covers all seven sections of a compliant ACoP L8 risk assessment. A low price may mean a low-quality document that would not hold up to inspection.

This guide covers legionella risk assessment costs and options for UK duty holders in 2026. Cost ranges are indicative based on market observation — actual quotes will vary by provider, region, and property complexity. This is general guidance, not legal or professional advice — for complex systems, consult a competent person as defined by ACoP L8.

Sources

• HSE — Legionella and landlords' responsibilities
• HSE — ACoP L8: Legionnaires' disease
• HSE — HSG274: Legionnaires' disease technical guidance