For a very rough pipe wall the friction factor is constant at high reynolds numbers. for a length l1 the pressure drop over the length is p1. if the length of the pipe is then doubled, what is the relation of the new pressure drop p2 to the original pressure drop p1 at the original mass flow rate?
i would think by taking all the water out and storing it somewhere else and filtering it or cleaning it then put it back
,a pencil being sharpened,exploding dynamite,and freezing water,