I have little experience with PE pipe for pressure. My recollection (so I go back 12 years) was that you butt weld the pe pipe as you install it and mobilizing the welder is big $ so push on PVC is more cost effective. (Also, I know how to install push on pvc, but welding PE for a pressure...
There are two things flow tests are good for - approximate assessment of system condition and identification of gross inadequacy. To perform the assessment on paper you need two flow rates and two pressures. Doing the test during the day means you have background flow, do it 3 a.m. and you may...
Don't extrapolate a curve... there's a reason the pump manufacturers stop drawing the curve where they do. If you have to pump at similar flows under both conditions, then install two different pumps - yes, thats means you spend nearly twice as much right off the bat, but if you don't you'll be...
To learn about pumps and pumping stations I would suggest "Pumping Station Design" by Jones, Sanks, Tchobanoglous and Bosserman... the book is eminently readable (not a snoozer so don't use it as a sleep aid) and you'll learn plenty. Then you have a more focused approach to your assignment...
