Only thru fire hose and not thru the water mains. Pumping water from a distanced water source (hydrant or static draft) to another apparatus that is called relay pumping. There is a wild difference in pressure when talking draft vs hydrant, but you are pumping the water at a pressure to overcome the friction loss inside of the hose x distance of the hose. Because I suck at explaining things, here is my best explanation Connect to a hydrant on corner of Avenue A and 1st street. Static pressure of the hydrant, which is the psi on my pump intake when not pumping anything, is 80 psi. The fire is 600’ down Avenue A on the corner of A and 6th street. We lay 600’ of LDH (supply line or large diameter hose) from the hydrant to the engine that is making the actual attack on the fire(attack pumper). I connect my intake to the hydrant, then connect the 600’ of LDH to my discharge. I then send idle pump pressure thru the 600’ of LDH that terminates at the attack pumper. I coordinate my pressure discharge with the attack engine via radio until he tells me he has 80psi on his intake. My discharge pressure will most likely be 160-ish depending on several factors, the size of the LDH we are using and the friction loss coefficient from the manufacturer; among several other factors. TLDR; you need volume AND pressure to move water. But when you have enough of one or the other, you can essentially move the water source directly to the scene of the fight, as long as you have competent operators and the equipment necessary to do so. I’ve been a part of a relay that was almost 2500’ and at the terminal end we were flowing in excess of 1700 gpm.