Before you buy
Do I need a legionella test?
For most homes and simple rental properties, no. HSE says testing is not usually required for domestic hot and cold water systems. Sampling is for situations where the normal controls are in doubt or the people using the building are at higher risk.
Last reviewed October 2026 against HSE guidance.
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What HSE says
“Testing or sampling for legionella (sometimes referred to as microbiological monitoring) is not usually required for domestic hot and cold water systems, and is only needed in very specific circumstances.”
HSE adds that testing should not be confused with temperature monitoring, which it calls a reliable method for confirming the water system is under control, and that the law does not require landlords to obtain or produce a ‘legionella test certificate’.
When sampling should be done
HSG274 Part 2 says legionella monitoring should be carried out where there is doubt about the efficacy of the control regime, or where recommended temperatures, disinfectant concentrations or other precautions are not being consistently achieved. The circumstances it lists include:
- systems treated with biocides where water is stored or distributed at reduced temperatures
- systems where the control levels are not being consistently achieved
- high-risk areas or buildings with susceptible people, such as healthcare premises and care homes
- a suspected or identified outbreak
For mains-fed domestic hot and cold water, the guidance says microbiological monitoring is not usually required unless the risk assessment or monitoring indicates there is a problem.
Quick guide
| Your situation | Is a test worthwhile? |
|---|---|
| Single let, combi boiler, used every day, temperatures fine | Not needed. Keep your risk assessment up to date. |
| Hot water will not reach 50°C at outlets, or cold is above 20°C | Fix the temperatures first. A test can then confirm the system is under control. |
| Property empty for several weeks | Flush thoroughly first. A test is optional reassurance before re-letting. |
| Holiday let or HMO with a hot tub or spa bath | Spa pools carry a higher risk and have their own guidance. Testing is commonly part of the control regime. |
| Care home, healthcare or residents at higher risk | Follow your risk assessment and sector guidance. Routine sampling is common. |
| An agent or insurer has asked for a test | It is their requirement, not the law's. A laboratory kit result will usually satisfy it; ask first. |
| Someone using the building has Legionnaires' disease | Do not rely on a kit. Take specialist advice immediately. |
What you must do instead
The legal duty is to assess the risk and keep it under control. For a rental property that means a simple risk assessment, sensible temperatures and avoiding stagnant water. Our sister site explains what landlords must do and offers a free template.
If you do decide to test, compare UK kits here.
Questions people ask
Is legionella testing a legal requirement for landlords?
No. HSE says testing is not usually required for domestic hot and cold water systems and that the law does not require a legionella test certificate. The legal duty is to assess and control the risk.
How often should I test for legionella?
There is no general interval for hot and cold water systems. Where sampling is needed, the frequency comes from the risk assessment. HSE's guidance gives examples such as monthly or weekly sampling where controls are not being achieved.
Should I test a property that has been empty?
Flushing is the essential step. HSE says outlets should be used at least once a week to stop water stagnating. A test after flushing is optional reassurance.
Sources
- HSE: Legionella and landlords' responsibilities
- HSE: HSG274 Part 2, The control of legionella bacteria in hot and cold water systems
Checked against these sources in October 2026. This page is general information, not legal advice.
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