Move water heater to location with smaller diameter pipes
Whether the 1/2&quot; dia pipe will provide sufficient flow depends on your requirements. Personally I would use it. The flow would supply any ordinary single shower head. I would recommend a hand holdable, low flow shower head with a flexible hose rated at say 1.5 gal/min (5 to 6 L/min). This would save energy and water while giving a fully adequate shower.
The 1/2&quot; dia pipe will mean that hot water from the heater will arrive at the shower quicker than with 3/4&quot; pipe. There will also be less water wasted and less hot water wasted by abandonment in the line.