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Thermostatic Mixing Valves UK

Thermostatic Mixing Valves UK

Thermostatic Mixing Valves UK


Is it a requirement to install thermostatic mixing valves on appliances (e.g. baths, showers, taps) in hotels in the UK?

If so, does it have to be a certain type? e.g TMV3

Thanks in advance,

RE: Thermostatic Mixing Valves UK

Thank you for your reply. That document and other documents say that is it "best practice" to fit them in hotels on baths, showers and basins but it is not a requirement under regulations.

It also says "Guidance to the Water Regulations (G18.5)". I have been searching for a download of this document. Do you know where I can find it?

RE: Thermostatic Mixing Valves UK

They don't work anyway. Always either way too hot, or way too cold. I like the two valves, mix it yourself method.

RE: Thermostatic Mixing Valves UK

Thermostatic valves were developed because there is an increased risk of scalding when using low water flow fixtures. At relatively low flow through shower/bath valves, temperature/pressure changes are felt much more acutely. It is also necessary to keep the water temperature high in institutional facilities to avoid bacterial contamination.

Thermostatic valves have two handles: one controlling the volume, one for the water temperature. This is because thermostatic valves react to the temperature, not the pressure of the water. With this valve, you can change the flow volume without affecting the temperature, which makes conservation easy.


RE: Thermostatic Mixing Valves UK


From my perspective, the thermostatic (T) shower valves were not developed because of low flow fixtures, but because the valves that controlled on pressure (P) alone would not account for the maintenance personnel changing the water heater outlet temperature after the limit stop on the valve had been set.

When there are complaints of no hot water, the maintenance personnel will be lazy and just turn up the water heater. One handle shower valves have a physical limit set screw that is supposed to be fixed during installation so the mixed hot water never exceeds the code limit. The problem is these valves are set with a certain maximum hot water temperature from the water heater. When the temperature is increased, that same limit stop now allows hotter water. So somebody turns on the water at the level they have always set it, but when they get in the shower, the water is hotter and that causes problems.

I could be wrong, but I don't know that water conservation played a part in their development.

As a specifier, I typically do not specify the (T) valves since they do not respond well (quick enough) to the pressure fluctuations in systems, i.e. the hot shower when somebody flushes a toilet. I am not familiar with the two handle (T) valves. The ones I have seen are smaller versions of the master mixing valves.

If I want to be extra cautious and the owner has no qualms of spending a bit more money, I will specify the T-P valves which will work on both temperature and pressure fluctuations.

I cannot speak to the UK requirements.

RE: Thermostatic Mixing Valves UK

Thanks all for replies. I have been sieving through (https://www.gov.uk/government/publications/sanitat...) provided above (thanks L") to get some clarification on the UK regulations.

In a nutshell a temp control is only required on a bath when there is one of the following material changes of use: where a building is used as a dwelling where previously it was not and where a building contains a flat where previously it did not.

Temp controls are not required on other appliances.

The above regulations change for NHS/care homes (blending valves are required).

If anyone else has read/can be bothered reading the regs it would be good to hear their interpretation also!...

RE: Thermostatic Mixing Valves UK


"Tom Konen, P.E., conducted research at Stevens Institute of Technology on the impact of shower temperature using a low-flow showerhead. Similar studies were conducted in plumbing labs across the country. What the studies showed is that with a full-flowing showerhead when there is a change in water pressure, the shower water temperature only rises a few degrees — in the 5° to 7° range. However, when a showerhead is restricted to 3 gpm, the spike in temperature is 35° to 45°. Thus, the water is hitting the temperature that causes scalds within a few seconds.

The scalding incidents also resulted in a change to the plumbing codes. The 1990 BOCA National Plumbing Code was the first model plumbing code to mandate pressure balancing or thermostatic mixing valves (since changed to compensating shower valves) for all showers."


RE: Thermostatic Mixing Valves UK


Interesting history.

3 gpm shower heads, at least commercially, have not been available for awhile.

When I think of "normal" flow showers, I think of 2 gpm. Low flow (to me) is 1.5 gpm.

So, I guess I am already in the potential scalding flow/pressure region, which is why I don't specify anything less than a pressure balancing shower valve.

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