In our house, the bathroom is situated on the ground floor.

We have a combi-boiler that heats the water when you turn on the
shower. The water pressure is quite high and the shower is hot.

When I lived in a previous house, it had a power shower that pumped
the hot water from an imersion tank. The power shower was great but
the hot water from the tank didn't last very long.

I'm looking at replacing the bathroom in the current house and would
like the best of both words - instant hot water (no imersion tank) but
also the power of a power shower.

I was wondering.......

Could you fit a power shower pump on the shower input and the pass the
hot water from the boiler through the pump and into an electric shower
unit. The water would be heated by both the boiler and the electric
shower.

I guess the only problem would be the speed of the pump. Too fast a
flow and the boiler / electric shower couldn't heat the water
sufficiently. Too slow and the water would be very hot.

It's a shame that no one has done a mini heater unit that could fit
under the bath that would heat the water and which contains a powerful
pump with say a digital controller (like the controllers on an
electric shower) situated on the wall in the shower that could be used
to control the exact temperature.

Graham