HTM 04-01 and TMVs in London NHS sites and private clinics

If you look after water safety in a hospital, a health centre or a private clinic, you'll have heard "HTM 04-01" more times than you've had hot dinners. It's the guidance everyone in healthcare water works to. Here's what it actually says about thermostatic mixing valves, in plain English, and how it plays out when the building is a Georgian townhouse on Harley Street rather than a purpose-built hospital wing.

What HTM 04-01 is

Health Technical Memorandum 04-01 is the Department of Health and Social Care's guidance on safe water in healthcare premises. The current edition comes in three parts. Part A covers design, installation and commissioning. Part B covers operational management. Part C deals with Pseudomonas aeruginosa, which matters most in augmented care units like ICUs and neonatal wards.

It's guidance rather than law in its own right. But it sits alongside the legal duties under the Health and Safety at Work etc. Act, COSHH and ACOP L8, and for NHS organisations it's the expected standard. Plenty of private hospitals, clinics, dental practices and care providers use it as their benchmark too, because it's the most thorough guidance around.

What it says about TMVs

Without reproducing the whole document, the main points for TMVs are these:

• Use TMV3-approved valves in healthcare settings where scalding is a risk.
• Keep the mixed water run short. Valves should be fitted as close to the outlet as practical, so there's as little warm water sitting in pipework as possible.
• Set temperatures for the outlet and the user. The figures commonly used for TMV3 valves are 41°C at showers and washbasins, 38°C at bidets and 44°C at baths, with your water safety plan setting anything different.
• Test after commissioning. New valves get in-service tests at around 6 to 8 weeks and again at 12 to 15 weeks.
• Set the interval from the results. After that, how often a valve is checked depends on how much it drifts. Stable valves can go longer; valves that move get serviced and stay on a short interval.
• Record everything. Temperatures, fail-safe results, parts replaced and the date the next check is due.

Who decides what on an NHS site

HTM 04-01 expects a proper management structure. There's normally a Water Safety Group overseeing a Water Safety Plan, a Responsible Person (Water) who manages things day to day, and an Authorising Engineer (Water) who gives independent advice and audits. Contractors like us work within that. We follow the trust's written scheme, permit-to-work system and infection control rules, and we hand back records in the format the estates team needs.

In augmented care, the Water Safety Group may have firm views on where TMVs go, which type is used and how outlets are flushed, because of the Pseudomonas guidance in Part C. That's their call, and we'll work to it.

Private clinics: same guidance, different building

Central London has a huge number of private clinics, consulting rooms and dental practices, especially around Harley Street, Wimpole Street, Marylebone and Fitzrovia. Many sit in converted townhouses with plumbing that's been extended, reworked and squeezed into tiny spaces over a century or more.

Those buildings bring their own challenges:

• Valves in awkward places. A TMV for a clinical hand-wash basin might be in a ceiling void, behind a duct panel or in the room next door. That can make the mixed water run longer than it should be, which is worth raising with whoever advises on your water safety.
• Shared buildings. Several practices in one house, sharing a hot water system none of them fully controls. Who's responsible for which valve needs to be clear.
• Mixed valve types from different fit-outs, not all of them TMV3 approved.
• Very busy diaries. Rooms are booked back to back, so we work early, late or between sessions.

Private clinics in England registered with CQC will want records that show their premises and equipment are safe. HTM 04-01 gives a well-understood way of doing that for water, even where it isn't strictly mandatory.

A typical scenario

Imagine a private clinic on three floors of a Marylebone townhouse, with eight consulting rooms, a minor procedures room and two accessible toilets. The practice manager knows there are TMVs but not how many, and the last records are patchy. A sensible approach would be a survey to find and label every valve, followed by servicing booked before the first appointments of the day across a couple of mornings. The clinic gets a register, a certificate for each valve and a schedule based on HTM 04-01's drift-based approach, ready for its next internal audit.

London water makes it harder

HTM 04-01 sets the interval by drift, and in London, drift often comes from scale. Our hard water clogs strainers, slows the thermostatic element and stops check valves seating properly. Healthcare sites here often end up on shorter intervals than the same building would need in a soft-water area. We've written more about this in hard London water and TMV limescale.

Where we work

We service TMVs across NHS and private healthcare buildings throughout London, with plenty of clinics in Central London. For care settings rather than clinics, see our post on care homes, TMV3 valves and CQC.

The short version

HTM 04-01 asks for TMV3 valves fitted close to the outlet, tested after commissioning, serviced at an interval set by how much they drift, and recorded properly. In London, add hard water and tricky old buildings to the mix. Get those basics right and your water safety group, your auditors and your patients will all be happier.

See our TMV compliance guide for more background, or TMV servicing for what each visit includes.