Minimum working pressure of bath/shower mixer

Hi 0.2 bar is a relatively low working pressure for a tap. You should be fine to have that mixer tap installed with your type of system.

For every meter fall is a bar of pressure so if you have 2 meter fall from you cold water storage this will be 2 bar of pressure. As for your hot water storage be sited on the same level then I am afraid your pressure coming out of the hot tap will be very weak.

Firstly you need to establish that your cold supply is tank fed also as equal pressures are required for a BSM. Where your HW cylinder is located makes no difference to the pressure you get, contrary to the comment above. It is the height of the CW storage tank in the loft that will govern the pressure available. The tap should function without issue but the height of the cold tank could be an issue if weak showering is experienced currently. If your old BSM has weak flow rate then it's very likely that the tank is pretty well at joist height. If this is the case then you may need to raise the tank to give a head of 1 metre or so. The higher the tank, the better the pressure. A pump is another option to consider. If you currently have problems mixing the hot & cold then it is likely that your cold supply is from the mains. In which case you would need a new supply pipe direct from the tank. Also it would be a good idea to check the connections to the taps under the bath. If they are flexis then make sure they are not twisted or kinked as this could also restrict the flow. I hope that has answered your question adequately.