Legionella testing or a risk assessment: what do landlords need?
"Legionella testing" is used loosely, and landlords are sometimes sold a water sample in the belief it is the legal requirement. It is not, and a sample answers a much narrower question than most people assume.
This guide sets the three activities side by side so you can see what each one actually tells you.
The short answer
Landlords need a Legionella risk assessment. Routine laboratory testing of the water is not usually required for domestic hot and cold water systems.
The HSE's guidance is that microbiological sampling of hot and cold water systems is reserved for specific circumstances rather than done as a matter of routine — for example where control measures are not working as expected, or where there is a specific reason for concern.
Temperature monitoring sits between the two: it is evidence that controls are working, and it is not a laboratory test.
General information, not legal advice. This guide describes the position in Great Britain. Northern Ireland is regulated by HSENI, and the Republic of Ireland has a separate legal framework — see the country pages.
The three activities compared
- Risk assessment
- Identifies the system, the conditions that could allow bacteria to multiply, how people could be exposed, and what controls are needed. This is the duty.
- Temperature monitoring
- Recorded readings at named outlets showing whether temperature control is working. Practical, cheap, repeatable, and the everyday evidence in a domestic system.
- Microbiological sampling
- A laboratory analysis of a water sample. Tells you about that sample, at that outlet, at that moment. Not routinely expected for domestic hot and cold water systems.
When sampling may be appropriate
- Where the risk assessment identifies a specific reason for concern that temperature control cannot resolve
- Where control measures are not achieving the conditions the assessment relies on
- Where a case of Legionnaires' disease has been associated with the property and is being investigated
- Where a competent specialist recommends it as part of a written scheme of control for a more complex system
- In systems outside the scope of simple domestic hot and cold water, such as spa pools
What a negative sample does not prove
A negative result means Legionella bacteria were not detected in that sample, from that outlet, on that day, by that method. Water systems change: an outlet falls out of use, a tenant leaves for three weeks, a thermostat drifts.
Treating a negative sample as lasting proof of safety is the most common misuse of testing. It is also why the duty is framed around assessing and controlling risk continuously rather than around producing a result.
What to do instead in a domestic property
- Carry out a proportionate, property-specific risk assessment
- Keep hot water hot and cold water cold, and record observations at named outlets
- Deal with stagnation: little-used outlets, dead legs, voids and unused rooms
- Keep shower heads and hoses clean and descaled
- Give the tenant clear, simple water-use information
- Review periodically and when something changes
How LegionellaWise describes readings
Every reading in a LegionellaWise report is labelled as temperature monitoring evidence tied to a named outlet, with its date and photo. Nothing in the report is presented as a laboratory test result or as proof that the system is free of Legionella bacteria.
Questions landlords also ask
Does a landlord need Legionella water testing by law?
No. Health and safety law requires the risk to be assessed and controlled. Routine microbiological sampling is not usually required for domestic hot and cold water systems.
Are DIY Legionella test kits worth buying?
For a simple domestic system they answer a question you were not required to ask, and a single result can create false reassurance. Effort is better spent on the assessment, temperature control and dealing with stagnation.
Is temperature monitoring the same as Legionella testing?
No. Temperature monitoring shows whether a control is working. Testing means laboratory analysis for the bacteria themselves. They answer different questions and should never be described interchangeably.
Who should take a sample if one is needed?
Sampling should be arranged through a competent specialist using an appropriately accredited laboratory, with the sampling point and method chosen to answer a specific question.
See whether guided self-assessment fits your property
The free suitability check asks a short set of questions about the water system, the building and the occupants, then tells you plainly whether guided self-assessment looks appropriate or whether the property should go to a specialist.
Official sources
- HSE — Testing and monitoring your water system
- HSE — Hot and cold water systems
- HSE — Legionella and landlords' responsibilities
- HSE — Approved Code of Practice and guidance L8
General information, not legal advice. Requirements and guidance differ between jurisdictions — check the country page that applies to your property.
Related reading
Do I need a certificate?
The HSE says health and safety law does not require a Legionella test certificate. What a report, monitoring and sampling each are, and why a record still matters.
Water temperatures
Common HSE reference points for hot and cold water, what a reading does and does not prove, and how to record one properly with TMV and scalding caveats.
Is it a legal requirement?
The duty is to assess and control the risk — not to buy a certificate or fill in a prescribed form. How that plays out across the UK and Ireland.
How to do the assessment
A step-by-step process for a simple domestic property, from competence and system description through to findings, tenant information and review triggers.