Originally Posted by mrbrightside11
Not 100% sure I think itâ€™s just mains fed but I will check with the plumber
Combi shower shouldn't be off the mains at all. Combi should be fed from cold water tank. It should be Pumped from tank to combi and the cold water for the shower, basin etc should be off the same pump.
If plumber didn't install a pump then he has it fed from mains most likely. As said above if its mains fed then you are very limited in what shower you have installed. Thermostatic showers require equal pressure on hot & cold inlet.
Depending on how far away from the bathroom the boiler is it's possible that an electric shower will be cheaper to run. The pressure won't be as good though