pumps efficiency???

is a pumps ACTUAL efficiency a factor of sheer vertical change or the amount of plumping used before outlet

for example a Mag Drive 3 flows 375 GPH at 0 feet according to http://www.marinedepot.com/aquarium_powerheads_pumps_danner_mag_drive_supreme.asp?CartId=

it also flows 270 GPH at 4 feet and 325 at 2 feet

now if one was to use 4 feet of tubing with only a 2 foot vertical rise would the flow rate be 270 or 325? and why?

sorry if anyone finds this boring but academic curiosity is getting the better of me atm

 

Head loss refers to the resistance against the flow of the pump output. decreasing pipe size restricts flow and thus rate. Gravity is another factor. If you push water higher than the pump, you lose flow rate. any angle the pipe is at, if it is up it is fighting gravity. As for the horizontal portion of your piping, once the pump gets the water moving, there is no large loss to your flow. So the horizontal part of your outlet is negligible and flow will be near to what the 2 foot vertical head will be.

Here is a calculator that will help you out with any flow question. it even allows you to insert your exact pump model so the flow calculations will be correct. you might find some other interesting flow charts listed on the left hand side. hope that helps.
http://reefcentral.com/calc/hlc2.php

 

wow cool site ... i was looking at the mag 7 for SWCD to use seperate from my return pump(closed system) and that would leave me looking at a flow rate of 515 GPH so i think that ought to work well

 

Yeah I used this site to figure out how to match my inlet pipe size for inflow to my refuge with the outlet return of a mag 7 with a 5 foot head, so the inflow closely matches the return flow. I thought this would help. Cheers.