pipe friction head loss Darcy-Weisbach
Water coming out weak at the end of a long pipe is because viscous friction shaved the pressure a little all along the way. See how the water height of the gauges stood along the pipe falls, by dragging the flow rate. The shaved height is the loss along the path.
Stand thin pressure gauges along the pipe and the water height steps down from the inlet to the outlet, and this height is the pressure head at that spot. Drag the flow rate and the more that flows the steeper the slope and the more it falls at the end. Viscous friction nibbles the energy of the flow little by little along the path. The steeper the steps, the thirstier the end.
The longer the pipe, the longer the distance friction acts, and the larger the loss by that much. Drag the pipe length L and the head loss grows in proportion, and if everything else is the same a pipe twice as long is twice the loss. So a supply pipe that sends water far loses more pressure. Friction does work for the length.
When the speed grows, the loss grows much faster. In turbulent flow the head loss is proportional to the square of the speed, and when you drag the speed v the curve shoots up as a parabola. Double the speed and the loss is four times, so if you raise the flow rate too hard the pressure runs short sharply. Speed grows the loss as a square.
All of this gathers in one Darcy–Weisbach formula. hf = f LDv²2g, the product of the friction factor f, the length-to-diameter ratio LD, and the velocity head v²2g. Drag the speed v and the bar of each term and the final hf move together, and the smaller the diameter D the larger LD and the loss jumps. A thin pipe makes the same length more expensive.
The friction factor f depends on how rough the inside of the pipe is. Drag the relative roughness εD and a smooth new pipe has a small f, while a rusty rough old pipe has a large f and the loss grows even at the same flow rate, which is what the Moody chart says. So an old line gives weak water at the end even with the same pump. A rough wall sends the same water at a higher price.