Emersion heater install

[Tash Jan]

I am fitting a 80 lt back up emersion, flat tank it's back up while I interview the existing gas boiler, mechanically not gas wise. I only have 14 mm pipes up stairs the run to shower is 2m for hot and cold pipes. There is no chance to fit a larger supply pipe. I am aware of press reduction Vale and temp control valve requirements and the required circuit. My q is should I run 20mm from 14mm at Bath, shower supply to the emersion or will the 14mm be OK it's to shower while boiler in bits

 

[ShaunCorbs]

What’s the feed pipe(size) to the immersion?