The pump manufacturers publish these specs. There is a way to calculate it, but I'm not smart enough. You could figure out the volume of water in the diameter of the tube, the height of the tube and calculate it's weight. But what that means to the motor of the pump, we don't know because we don't know the pump specs. Eheim is really good about publishing head specs... at least in their hobby line of pumps.
Go to www.aquatraders.com Click on fliters and skimmers. Click on External Filters. Look for the one called "CFS 500".
