does anyone have a chart or know an equation to work out how pressure will improve over the length of the pipe. We have installed an unvented cylinder in a loft and have 14lpm with water softner connected. 18lpm without. 2.2bar pressure at shower upstairs. Customer wants more pressure as they have 25lpm at tap downstairs. 4.5bar pressure. Confirmed by water board apparently. The main runs up to the cupboard in 15mm so we are looking to find out what the lpm gain would be if we were to upgrade the 15mm pipe to 22mm. I wondered if anyone had a sum to work it out. I.e every mtre in height of 22mm pipe will reduce the flow rate from at the tap by 0.5lpm or something like that? Many thanks in advance!