Hi,
I got one of these thermostatic mixing valves last weekend to limit the water temperature at the hot taps in two rooms in our house which are used for childcare.

I was very suprised to find that the cold water feed to the unit very quickly heated up and convection soon resulted in the whole cold pipe from the attic tank to the mixing valve getting hot! This in turn means that the cold storage tank in the attic is also being heated!

Is it just me, or is this a major design flaw and waste of energy?

I'm also curious to know whether I could fit a non-return valve on the cold feed to the mixing valve to cure the problem?

Thanks, and sorry for so many questions today!

Paul

It could be calcium (limescale) build up on the check valves seats preventing the valves from returning to their closed positions.

If you live in a hard water area, then it might make sense to install a water conditioner adjacent to your TMV.