"BenignVanilla" m
wrote:

I plan on piping water from the reservoir to the VF using 4 inch pipe. What
about the return? If the pump only has a 2 inch output (for sake of
argument) does the size of the outflow pipe matter? Should I go with 4 inch
on the return and step down to whatever the pump is putting out?

Larger than the output of the pump. It doesn't have to be real big,
cause as it has been pointed out that area increases as a square factor
of pipe radius, so usually one pipe size.