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TMV compliance, explained in plain English
There's no single "TMV law". Instead there's a mix of general duties, healthcare guidance, product standards and certification schemes. Here's how they fit together, and what they mean for your valves.
- General dutyHSWA 1974
- Healthcare guidanceHTM 04-01
- Valve standardsBS EN 1111 / 1287
- LegionellaACOP L8 · HSG274
Where the duty comes from
If you run a building, the Health and Safety at Work etc. Act 1974 means you have to manage reasonably foreseeable risks to the people using it. Scalding from hot water is one of those risks, and it's taken especially seriously where people are vulnerable: older residents, patients, young children and anyone with reduced feeling or mobility.
HSE guidance for health and social care says that where vulnerable people could be exposed to hot water, the temperature at outlets they can use should be controlled, usually with a TMV. In other buildings it's a question for your risk assessment.
HTM 04-01 and in-service testing
HTM 04-01 is the Department of Health and Social Care's guidance on safe water in healthcare premises. It covers TMVs in some detail, including how they're specified, commissioned and tested once they're in use. Lots of care providers and other organisations follow it as good practice, even outside the NHS.
The general approach to in-service testing is:
- Commission the valve and record the baseline readings.
- Test it again in the first few weeks, and again a few months after installation.
- If the readings are stable, set the ongoing test interval from those results.
- If the mixed temperature has shifted noticeably, service the valve and test more often.
In practice that usually means a test at least once a year, and every six months in many care and healthcare settings. The exact interval for your site should be set out in your water safety plan or written scheme, and it's worth checking the manufacturer's instructions for each valve too.
Typical maximum mixed water temperatures
These are widely used maximum set points for TMVs serving vulnerable people. Your risk assessment, the valve's certification and the type of user might call for something different, so treat them as a guide rather than a rule.
| Outlet | Typical maximum | Notes |
|---|---|---|
| Bidet | 38°C | Lower set point for direct contact with sensitive skin. |
| Shower | 41°C | Whole-body contact, often with no way to step out quickly. |
| Washbasin | 41–43°C | 41°C is often used where hands are washed under running water. HSE care guidance refers to 43°C at washbasins. |
| Bath | 44°C | Set for bath fill. Temperatures should still be checked before anyone gets in. |
In new homes, Building Regulations Approved Document G limits the temperature of water to a bath to a maximum of 48°C. That's a separate requirement aimed at dwellings, and it's higher than the figures above, which are aimed at people who are more at risk.
BS EN 1111, BS EN 1287, TMV2 and TMV3
BS EN 1111
The European standard for thermostatic mixing valves on high pressure systems (PN 10). It sets out how the valve must perform, including how it responds to changes in supply.
BS EN 1287
The equivalent standard for low pressure thermostatic mixing valves, typically on gravity-fed systems.
TMV2 scheme
An independent third-party certification scheme for valves used in domestic-type settings. It uses BS EN 1111 and BS EN 1287 as its basis, with some extra UK requirements.
TMV3 scheme
A certification scheme for valves used in healthcare and care settings, based on the NHS performance specification. TMV3 valves are the ones expected under HTM 04-01.
A valve marked TMV2 or TMV3 has been tested for certain applications and pressure ranges. Check the certification covers the way you're actually using it. More on this in TMV2 vs TMV3: which valve do you need?
Why your TMVs belong in your Legionella plan
The Approved Code of Practice L8 and HSE's HSG274 guidance set out how to control Legionella in water systems. The main temperature controls are hot water stored at 60°C or above, hot water reaching outlets at 50°C or more (55°C in healthcare) within a minute, and cold water below 20°C within two minutes.
TMVs let you keep those temperatures in the system while making water safe at the tap. The trade-off is the short run of warm water after the valve, which is why HSG274 and HTM 04-01 both care about TMV position, flushing and maintenance.
- Fit TMVs as close to the outlet as practical
- Keep strainers clean and valves serviced
- Flush little-used outlets as your scheme requires
- Record supply and mixed temperatures at each test
- Review the need for each TMV in your risk assessment
What good TMV records look like
If something goes wrong, or an inspector visits, your records are how you show the valves have been looked after. They should be easy to find and easy to follow.
- A register of every valve: ID, location, make, model, type and outlet
- Commissioning readings for each valve
- Date, supply temperatures, mixed temperature and fail-safe result for every test
- What was done: cleaned, descaled, recalibrated, replaced
- Anything outstanding, and when it was put right
- The next due date
Questions we get asked a lot
Is it a legal requirement to have TMVs?
There isn't one law that says "fit TMVs". But you do have a legal duty to manage scalding risk, and in care and healthcare settings HSE expects hot water at outlets used by vulnerable people to be temperature-controlled. In new homes, Building Regulations set a maximum temperature for bath water.
Does HTM 04-01 apply to care homes?
HTM 04-01 is written for healthcare premises. Care homes aren't strictly covered, but many follow it as good practice, and HSE's health and social care guidance points in the same direction.
What temperature should a TMV be set to?
It depends on the outlet and the user. Typical maximums are around 38°C for a bidet, 41°C for a shower, 41–43°C for a washbasin and 44°C for a bath. Your risk assessment might set something different.
Who can test and service TMVs?
Someone competent to do it, with calibrated instruments, who knows the valves and the guidance. They should record the results properly so you have evidence the work was done.
Related articles
Bringing TMVs back after a quiet spell or shutdown
Christmas closures, empty rooms and refurbs all leave valves sitting idle. What to check before people start using those outlets again.
Read the articleCommissioning a new TMV: what should happen on day one
A new TMV is only as good as the way it's set up. What should happen when a valve is commissioned, and the paperwork you should get afterwards.
Read the articleTMV asset registers: what auditors want to see
When someone asks to see your TMV records, a tidy register answers most of their questions before they've finished asking. What to put in one.
Read the articleNot sure if your valves are compliant?
Send us what you've got, even if it's patchy. We'll tell you where you stand and what needs doing.