Do I need legionella testing in a rented property?

No. There is no legal requirement to test the water in a rented property for legionella. What the law requires of a landlord is a legionella risk assessment of the water system and control of any risk it finds. Testing, meaning sending water samples to a laboratory, is something the assessment occasionally calls for, not a standing duty. For the great majority of rented houses and flats, a competent assessment plus simple temperature and flushing controls is the whole job.

The confusion is understandable, because the word "testing" gets used loosely for everything from running a tap and taking its temperature to couriered laboratory samples. It is worth separating the three things that get tangled together, because the law treats them very differently.

Assessment, monitoring, testing: three different things

The risk assessment is the legal duty under the Health and Safety at Work etc. Act 1974 and the management regulations, with ACOP L8 setting the expected standard. It is an inspection of the system and its use: where water is stored, whether it can stagnate, whether temperatures stay out of the growth range, and who might be exposed. Every landlord needs one. Our page on who is responsible for legionella in rented property sets out how the duty sits between landlord, agent, and tenant.

Monitoring is the routine that keeps the assessment live: checking hot water reaches 50°C at outlets, keeping cold below 20°C, flushing outlets before and after void periods, and recording it all. Monitoring uses a thermometer and a log book, not a laboratory.

Testing (sampling) sends water to a laboratory to culture legionella and report a count in CFU per litre, read against the action levels in HSG274's sampling guidance. It answers a specific question: are the bacteria actually present, and at what level. It is a diagnostic, not a control, and a clear result certifies nothing beyond that sample on that day.

Why routine testing is usually unnecessary in a rental

Legionella control in a typical domestic let works by removing the conditions the bacteria need, and those conditions are observable without a laboratory. A combi boiler heats water on demand so nothing sits warm in storage. A well-maintained cylinder holds water at 60°C and delivers it at 50°C or more. Mains-fed cold water arrives cool. If the assessment confirms the system is arranged that way, there is no warm stagnant water to test for, and a laboratory count would add cost without adding control.

The HSE's position for landlords reflects this: keep the assessment simple, proportionate, and reviewed when things change. The risk in most rentals is managed with knowledge and routine, not with sampling.

When sampling is the right call

Testing earns its keep when the assessment cannot close the question. Consider it where hot water persistently fails to reach temperature and the cause is unclear, where a converted building has shared tanks or a complicated system serving several flats, where a tenant is known to be especially vulnerable, or where you have had a positive result and need to verify that disinfection or repair has worked. In those cases the sample tells you something you cannot establish with a thermometer alone, and the result feeds straight back into the written scheme of control.

Beware the "annual legionella test" sales pitch

A small industry has grown up around telling landlords that annual legionella testing, or a "legionella certificate", is a legal requirement. It is not. There is no legionella certificate in UK law, and no requirement to sample a domestic rental on any schedule. What you can be asked to produce, by an insurer, an agent, or in the worst case an investigator, is evidence that you assessed the risk and acted on it: the assessment itself, your temperature and flushing records, and notes of any remedial work.

What you actually need to do

For most landlords the practical list is short. Assess each property's water system once and review it when the system or the tenancy changes. Keep hot water hot and cold water cold. Flush the whole system before a new tenancy after any void, and make sure tenants know to report problems with hot water and to clean their shower head. Write everything down and keep the records for at least five years. The free risk assessment builder walks you through the assessment for a rental and produces the record, and our landlord guide covers the duty end to end.

If the assessment leaves you unsure whether the risk is controlled, that uncertainty, not a calendar, is what justifies calling in sampling or specialist help.