I never thought about the reason for the gooseneck. It would not collect water or sediment, as the line is small enough to pull the contaminants on down the line. It is probably to allow any leaks from the fitting to drip straight down to the ground, rather than running along the line and accumulating on the frame and body?!? Filter is a must...I can see arguments for suction or pressure side. Either way, it won't matter for a good filter, and a clogged one will stop the flow.