Guide
Legionella testing vs risk assessment: which you actually need
Updated
Assessment and testing get sold as a bundle, but the law asks for one of them and only sometimes the other. Paying for sampling you do not need is the most common overspend in this market.
Two different products
- Legionella risk assessment
- A survey of the water system and how it is used: stored water, temperatures, dead legs, spray-forming outlets, occupancy. This is the legal duty under HSWA 1974 and COSHH via ACOP L8, and it is what typically costs £60–£150 for simple premises and £200–£600+ for complex ones (typical 2026 quotes).
- Legionella testing (sampling)
- Taking water samples for laboratory culture analysis, priced per sample. It is a monitoring control measure, used where the risk assessment or written scheme calls for it, not a legal requirement in its own right for most premises.
When testing is appropriate
- Cooling towers and evaporative condensers: routine sampling is a standard part of the written control scheme, on the frequencies set out in HSG274 Part 1.
- Where control is in doubt: temperatures out of range, biofilm suspected, after remedial cleaning and disinfection, or following a case of legionellosis.
- Higher-risk settings such as healthcare premises with susceptible occupants, where the written scheme specifies sampling.
- Not, usually, domestic hot and cold water systems: HSE states testing is generally unnecessary in domestic premises; the assessment and simple controls are the requirement (HSE legionella guidance).
How to buy in the right order
- Buy the risk assessment first. It is the legal duty and it tells you whether sampling has any job to do on your system.
- Let the written scheme drive any testing: what is sampled, where, how often, and what happens when a result is positive, testing without an action plan is money spent on numbers nobody will act on.
- Keep the records together: assessment, scheme, monitoring results, remedial actions. That file is what an inspector or a court asks for.
A quote that leads with sampling for a small office or rented flat, before any assessment has been done, has the order backwards. Get assessment prices first via the form and add testing only where the assessment says so.