Hot water problem

[topgun]

I am currently re-routing the hot water pipes in my bathroom and I have come accross a T juction in the hot water supply (of a combi boiler) that goes to the cold water main, has anyone any idea what this could be and if I actually need this. I think it could be some sort of safety device to cool water if the temperature gets to high. please help.

 

[Richard C]

If could be a Thermostatic Mixing Valve (TMV) but this looks very different to a normal pipe tee & most have some form of adjustment on the top. TMV’s are fitted for 2 reasons
1. As a safety feature to prevent accidental scalding.
2. Some ancillary devices (shower booster pumps) have a maximum working temperature of 60-65 degrees to avoid damage.

I don’t know if the pump in a combi boiler has a maximum temperature restriction but I’d be wary of removing the TMV (if that’s what it is) without checking.

Try posting in the plumbing/heating forum, which is where this should be really!