I contracted a local company to install two bathrooms in a ground floor flat which has high incoming mains water pressure with hot water provided by a mains pressure unvented Oso boiler. One bathroom has been completed, but the thermostatic mixer shower installed - a Tre Mercati concealed unit (model no. 83052) - a brand I had never heard of before, does not regulate the water temperature as it should. It only gives cold water, or after adjusting by the fitters, only warm water, but not both. Is this appliance compatible with a high pressure system? They now want to install a pressure reduction valve upstream of the supply to this bathroom. Will this not affect the whole equilibrium of the system when both bathroom showers are being used at the same time?
Hi there could be many answers to your problem
The valve might be faulty
The pressure to high for the valve
If the water pressure is to high for the shower valve you could fit a inline reduction pressure valve to water inlet on the shower line only not to the whole system
Sounds like it may need a thermostatic regulator valve fitting or if fitted, adjusting
You need to balance the system normally on a pressured hot water cylinder there is an outlet to provide cold water to the showers at same pressure as hot water connection will be on the reducing valve on the cold feed into the cylinder
When you have a unvented hot water cylinder, it comes with a combination valve, on that valve it has a connection for cold water to other services ( for the purpose of achieving balanced hot and cold water, so pressures are equal) the other possibilities are pipes are the wrong way round on shower mixer, most showers for high pressure also come with restricters that you can fit in the the valve, in the case of unbalanced hot and cold water pressure
If you do not know, and they do not know find a plumber who does.
You need to check the range of water pressure the Shower Valve works under and then check what the mains pressure is and if this is in within tolerance of valve then a faulty valve or if outside range then incorrect shower valve fitted
Not sure of the model easy enough to google and it will state works on high pressure and yes fitting a pressure reducing valve should cure the issue , just check hot and cold supplies are not the wrong way around entering shower valve, simply ask the question and also make sure that when shower turned to hot only you get only hot water.