Buildings don't run at the same pace all year. Offices close over Christmas. Schools empty out for the holidays. Hotels have a quiet season, care homes have rooms standing empty between residents, and refurbishments can leave whole floors out of action for months. Through all of that, the TMVs and the pipework around them just sit there, full of water that isn't moving.
When people come back, those outlets need a bit of attention before anyone uses them. Mid-January, with sites reopening after the festive break, is a good moment to talk about why.
What happens to an idle TMV
Two things, mainly.
The water goes stale. A TMV delivers blended water, usually around 41°C, or a little more for a bath. That's comfortable for washing, and unfortunately it's also comfortable for Legionella bacteria. In normal use, the water in that short run after the valve is replaced every time someone turns the tap on. When nobody does, it sits warm and still, which is exactly what you want to avoid.
The valve itself can stiffen up. The thermostatic element and shuttle are designed to keep moving. Leave them still for weeks, particularly in a hard water area, and scale or debris can settle and make them sluggish. A valve that tested perfectly before a shutdown won't necessarily behave the same way afterwards.
What the guidance says about little-used outlets
Under ACOP L8 and HSG274, you're expected to manage stagnation as part of Legionella control. HSG274 recommends that little-used outlets are flushed regularly, generally at least weekly, and your written scheme should say which outlets count as little-used and who flushes them.
For planned shutdowns, the best approach is to keep that flushing going while the building is quiet, so stagnation never gets a chance to build up. Where that hasn't happened, the outlets need flushing and checking before reuse, following your written scheme and your Legionella risk assessment. In some cases, after a long or uncontrolled shutdown, your water safety advisor might recommend further steps such as cleaning, disinfection or sampling.
Healthcare premises have their own detailed expectations in HTM 04-01, and care providers often follow a similar approach.
A sensible checklist before reuse
Every site is different, and your written scheme comes first. But for TMVs specifically, this is the kind of routine we'd expect to see:
- Check the hot water system is back up to temperature. TMVs need a properly hot supply to work as designed, and the hot water temperatures are a key Legionella control in their own right.
- Flush each outlet as set out in your written scheme, taking care not to create spray that people could breathe in.
- Measure the mixed temperature at the outlet with a calibrated thermometer and compare it with the set temperature.
- Do the fail-safe test. Isolate the cold supply and check the valve shuts down, then restore it and check the temperature settles.
- Deal with anything that's off. Valves that are sluggish, out of temperature or fail the fail-safe test should be serviced before the outlet is used. If the fail-safe test fails, take the outlet out of use.
- Record it. What was flushed, when, by whom, and the readings for each valve.
If your valves were due a routine test around the same time, it often makes sense to combine the two and do a full test and service before reopening.
Rooms and flats left empty
It isn't only whole-building shutdowns. A care home room left empty for several weeks between residents, a hotel wing closed for the winter, or a void flat in a sheltered scheme are all the same problem on a smaller scale. The risk is that because the rest of the building is busy, nobody thinks about the one bathroom that isn't.
The fix is usually procedural: make sure empty rooms are on the flushing list, and make TMV checks part of getting a room ready for its next occupant. A quick temperature check and fail-safe test before someone new moves in is a small job that avoids a lot of worry.
After refurbishment
Refurbishments are a special case because the system has often been drained, altered or added to. Debris from the works can end up in TMV strainers, and new pipework changes the pressures and temperatures the valves see. New TMVs need proper commissioning, and existing ones that stayed in place should be tested and, if necessary, serviced before handover. Make sure any new valves are added to your asset register too.
A typical scenario
Imagine an independent school that closed for two weeks over Christmas. The premises team kept up weekly flushing of the boarding house showers, but the junior block washrooms were missed. On the first day back, before pupils arrive, the junior basins are flushed and each TMV is tested. Most are fine. One is reading noticeably warm and another is slow at the fail-safe test, so both are taken out of use and serviced that morning. The flushing gap goes on the agenda for the next water safety meeting.
Plan it before the next closure
The easiest way to handle a shutdown is to plan for it in advance. Put flushing on the rota for every closure, decide who does it, and book any TMV testing for the days before people return. It's far less hassle than discovering a problem on the first busy morning.
If you'd like help, we can test and recommission valves ahead of a reopening. See what's included in our TMV servicing and our TMV compliance guide, or read hard water and TMVs if your valves tend to stiffen up.
Reopening after a quiet spell?
Tell us what's been shut down and for how long. We'll test and recommission your valves so outlets are ready when people come back.