I have installed a shower mixer tap to a cold mains supply and the hot to the water tank supply and the pressure don't marry together so don't work properly. Is there a way round this?we are desperate for a shower because my missus finds it very difficult to get in bath due to arthritis. Much appreciated mark.

Assuming that you are in EU or UK.

In the US the mains supply provide water to the water heater and to all taps, therefore water pressure is always the equal. Is that the same for you?

In the US most currently sold tub and shower valves are single handle. All currently sold, single lever tub and shower valves have a pressure regulating valve. This pressure regulating valve is sometimes referred to as a temperature balancing valve. It is not really a temperature regulating valve but regulates temperature by balancing the water pressure. It is adjustable.

Some tub and shower valves have integral stop valves. These are accessible only with the escutcheon removed. If your new tub and shower valve has integral stop valves, are they both fully open?

If you new tub and shower valve has a pressure regulating valve, have you tried adjusting.

Assuming that you are in EU or UK.

In the US the mains supply provide water to the water heater and to all taps, therefore water pressure is always the equal. Is that the same for you?

In the US most currently sold tub and shower valves are single handle. All currently sold, single lever tub and shower valves have a pressure regulating valve. This pressure regulating valve is sometimes referred to as a temperature balancing valve. It is not really a temperature regulating valve but regulates temperature by balancing the water pressure. It is adjustable.

Some tub and shower valves have integral stop valves. These are accessible only with the escutcheon removed. If your new tub and shower valve has integral stop valves, are they both fully open?

If you new tub and shower valve has a pressure regulating valve, have you tried adjusting.
Hot water goes from boiler to tank. I live in England great Britain.
Watet pressure is not the same? We have brought the twin turn taps not single lever would that make any difference?would there be a pressure regulating valve inthere?

would there be a pressure regulating valve inthere?

Not likely.

Hot side pressure should be that same as hot side at other taps.

Check for integral stop valves. Do you know what to look for?

Turn off water. Remove the hot side stem from valve. Briefly turn on the hot water and flush out the hot side of the valve to remove any possible debris.

What kind of pipe? If you have copper pipes and made soldered connections you could have excess solder trapped in the valve.