I have an unvented HW tank and the input pressure reduction valve is set to a manufacturer recommended 2.1 bar (the main is 3 bar), so there is really no way to increase the tank pressure even if a cold water boost pump was fitted to the main.
My problem is that the tank is at the bottom of a 4 storey house and pressure/flow is insufficient at the top of the house. So my question is: could a boost pump be fitted to the outlet of the HW tank to help take the hot water to the top of the house?
If that is not a practicable solution, how else could I fix the problem?