Oberdorfer™ centrifugal pumps have a single rotating metal impeller. Liquid enters at the center and is thrown outward radically by centrifugal force. The impeller is not in contact with other pump parts resulting in quiet, efficient, pumping action. The flow produced is not positive which permits the discharge line to be shut off completely without danger of overloading motors or bursting lines. Consequently a relief valve is not required. The liquid flow varies directly as the pump speed--the higher the speed the greater the flow. Horsepower required varies directly as flow and pressure. Maximum horsepower is required with a wide open discharge line. This is the point of maximum flow. With a throttled discharge, the flow decreased at a greater rate than the pressure increases thereby requiring less horsepower at the higher pressures. This is known as an “unloading” feature of the pump. Silent, efficient, centrifugal pumping is ideal for convenient equipment location in offices, laboratories, public areas, and living quarters. Long trouble-free service life has made centrifugal pumps acceptable for industrial uses or wherever clean or contaminated liquid is to be transferred or handled. The 800B centrifugal pump has external ball bearings isolated from the liquid being pumped. The ball bearings are grease sealed for life requiring no maintenance.