Hi Snickster, by "percentage" I mean the ratio of frictional losses (in meters of fluid column) to the length of the pipe or it would also be understood as head gradient.
In my experience in pipeline design, it has always been said that the maximum recommended friction loss for water pipes is 5%. The recommendation is not to exceed this value. But what would be the source of this recommendation? Is it in an ASME standard or an ANSI/HI standard? There are hundreds...