A brand-new TMV straight out of the box isn't ready to protect anyone. It needs to be fitted in the right place, set up for the outlet it serves, tested, and recorded. That process is called commissioning, and it's the foundation for everything that follows. Every future test on that valve gets compared with the readings taken on day one.
Summer is peak season for new valves. Schools refurbish washrooms over the holidays, care homes update bathrooms, and plenty of buildings get works done while things are quieter. So here's what should happen when a TMV is commissioned, and what you should expect to get afterwards.
Before the valve goes in
Check it's the right valve
Commissioning starts before anything's fitted. The valve should be certified for the job it's doing: the right scheme (TMV2, TMV3 or both), approved for that outlet type, and suitable for the system pressures. A valve certified for a basin isn't necessarily approved for a bath, and one designed for high pressure may not perform on a low pressure gravity system. Our TMV2 vs TMV3 guide covers the schemes, and BS EN 1111 and BS EN 1287 cover high and low pressure valves respectively.
Check the position
The valve should be as close to the outlet as practical, so the run of blended water after it is short. That's important for Legionella control under HSG274, and it's something HTM 04-01 pays attention to in healthcare. It also needs to be reachable for future testing and servicing, ideally with isolation valves on both inlets.
Flush the pipework
New and altered pipework is full of debris: swarf, flux, bits of PTFE tape and general muck from the works. If that's flushed through a new TMV, it lands straight in the strainers and can damage the valve before it's done a day's work. The supplies should be flushed thoroughly before the valve is connected.
On the day: setting it up
Measure the supplies
The engineer should measure the hot and cold supply temperatures at the valve, and check the pressures are within what the valve is designed for. The hot supply needs to be hot enough for the valve to work properly. Most manufacturers specify a minimum difference between the hot supply and the mixed temperature, and that's worth checking against the instructions.
Set the mixed temperature at the outlet
The temperature is set and measured at the outlet, where people actually use the water, not at the valve. It should be measured with a calibrated thermometer, with the outlet running at its normal flow. Typical maximums are 41°C for a shower, 41°C for a basin where hands are washed under running water (some guidance uses 43°C), and 44°C for a bath, with 46°C quoted in healthcare guidance as the maximum for bath fill. Your risk assessment may set specific figures.
Do the fail-safe test
With the outlet running at its set temperature, the cold supply to the valve is isolated. The valve should shut down quickly, cutting the flow to nothing or a trickle, within the limits in its certification and the manufacturer's instructions. Then the cold is restored and the engineer checks the temperature recovers to its set point.
If a brand-new valve fails this test, it doesn't go into service. Something's wrong with the valve, the installation or the supplies, and it needs sorting before anyone uses that outlet.
Lock the setting
Once it's set, the temperature adjustment should be secured so it can't be casually changed. Most valves used in public and care settings have a tamper-resistant adjuster or cap for this reason.
The paperwork you should get
Commissioning isn't finished until it's written down. For each valve you should receive a record showing:
- Where the valve is and which outlet it serves
- The make, model and certification
- The hot and cold supply temperatures
- The set mixed temperature at the outlet
- The fail-safe test result and the temperature after recovery
- The date, the engineer, and the thermometer used
Those readings are the baseline. Without them, nobody can tell later whether the valve has drifted or was simply set wrong. The valve should also be labelled and added to your asset register.
After day one: early checks
This is the bit that often gets forgotten. HTM 04-01 doesn't just ask for commissioning and then an annual test. It asks for in-service checks in the weeks and months after installation, so you can see how the valve behaves once it's in real use. The results of those early checks are then used to set the ongoing interval, which should be at least annual. A valve that holds steady can go onto a longer routine. One that's already moved needs attention and closer watching.
The simplest way to make sure those checks happen is to book them at the time of commissioning. We go into how intervals are set in how often should TMVs be serviced?
A typical scenario
Imagine a primary school having its infant toilets refurbished over the summer holidays. The plumbing contractor fits new TMV3 basin valves, and the premises manager wants to be sure they're set up properly before September. A proper commissioning visit would flush the new pipework, set each valve to 41°C at the tap, carry out a fail-safe test on every one, label them, and hand over a record sheet for each. The first in-service checks get booked for October half-term.
Getting it right from the start
Commissioning is a small part of the cost of a new valve, but it's what makes the valve trustworthy. If you're planning new TMVs, or you've had valves fitted and never received commissioning records, we can help. See our TMV installation page, our TMV compliance guide, or read repair or replace? if you're weighing up old valves.
Fitting new TMVs this summer?
Tell us how many valves and where. We'll supply, fit and commission them properly, and give you the records to prove it.