Thermostatic mixing valves in baths

[XanderHarris]

Do these need to be fitted on all baths, even if supplied by a combi. Or is it still just for stored hot water? Thanks

 

[Deleted member 267285]

The requirement is that hot water feeds to a bath must not exceed 48 degrees, no mention of type of delivery.

 

[EFLImpudence]

Just interested:

Does the wording on the right hand side mean that after the building is erected, G3(4) no longer applies and/or

if not formed by change of use it does not apply in any case?

 

[Deleted member 267285]

Just interested:

View attachment 303032

Does the wording on the right hand side mean that after the building is erected, G3(4) no longer applies and/or

if not formed by change of use it does not apply in any case?

No, it means that once installed, the way it’s preventing exceeding temperatures (usually a thermostatic mixing valve - TMV2/3) is provided upon when built, for example a new build, is maintained, and should be written in the building regulations part G3, the same regs that apply to the installation and maintenance of unvented hot water cylinders. They don’t apply to retrofit circumstances.

 

[fixitflav]

No, it means that once installed, the way it’s preventing exceeding temperatures (usually a thermostatic mixing valve - TMV2/3) is provided upon when built, for example a new build, is maintained, and should be written in the building regulations part G3, the same regs that apply to the installation and maintenance of unvented hot water cylinders. They don’t apply to retrofit circumstances.

Interesting. Does it mean the water from a hot tap (no mixer, separate H&C taps) must not exceed 48°C? That's how it seems to read, but HW is usually somewhat hotter than that.

 

[Madrab]

Does the wording on the right hand side mean that after the building is erected, G3(4) no longer applies and/or

if not formed by change of use it does not apply in any case?

The way we interpret the regs is that it applies to new builds or newly created bathrooms where there wasn't one before. When a bath is installed into one of these, it must now have a TMV2/3 rated mixing valve installed on the feed to the bath to ensure the water in the bath cannot exceed that set temp. It also means that once one is installed (as per the regs) and if it fails then it must be replaced (as per the regs) and not just removed, so yes the regs will still apply.

The system is designed to control the max temp that can be delivered out of the tap into the bath. It's to prevent scalding. In the case of separate taps/mixing taps, the HW must have a TMV inline to reduce the HW to a max of 48Deg, they're usually fitted below the bath.

 

[fixitflav]

The system is designed to control the max temp that can be delivered out of the tap into the bath. It's to prevent scalding. In the case of separate taps/mixing taps, the HW must have a TMV inline to reduce the HW to a max of 48Deg, they're usually fitted below the bath.

OK thanks, we live and learn!

 

[denso13]

Does it mean the water from a hot tap

Bath only, and they do need serviced, which they very rarely are.

 

[fixitflav]

Bath only, and they do need serviced, which they very rarely are.

I was just thinking of bath hot taps, but I see what you mean.

 

[XanderHarris]

Thanks a combi would only get it above 48c in the summer. With a 35c rise it needs the incoming water to be above 18c. I'm sure when I did college level 3. 2015/2017 that it was just for storaged water. But this appears to have changed?

 

[denso13]

But this appears to have changed?

Not sure if it has changed but the TMV is supposed to be a cover all, with the bath being the dangerous bit, hence why bath only.

 

[Deleted member 267285]

2015/2017 that it was just for storaged water. But this appears to have changed?

The building regulations that these are applied to are from 2010.