SalahiAndSon wrote:

When you see a pump head rateing is this for output length only or both
input and output length combined? Iwaki pumps are rated at a specific gph at
a 4' head. I have 3.5' from the sump to the pump and 4' on the output side
to my tank. is this considered a 7.5' head or does the head rateing only
apply to the output side? Could someone please explain this or maybe point
me to a site or equation to make it simple. Any advice would be greatly
appreciated.
thanks
G.

Head, applies to the return line (line from pump to tank). It is
the vertical distance the pump must lift the water.
If the opening if the return line is submerged below the tank water
surface, then the vertical distance is measured from the surface of
the water in the sump to the surface of the water in the tank
(measured straight up and down vertically). If the return line
discharges above the tank surface, vertical measure from the sump
water surface to the top rim of the tank should be sufficient for
comparison to the pump flow chart.
The chart on the pump box typically does not account for flow
losses due to fittings (elbows, spray bar and such) and friction loss
of the hose.
http://www.aquatext.com/tables/frict-wat.htm
shows some scary looking calculations for friction loss, but the
easiest way to overcome losses is by using over sized hose and "long
sweep" fittings.

HTH
Paul