The Capacity of the pump varies directly with speed but remain constant against pressure. however due to running clearance between the casing & impeller some liquid always bypasses to suction causing sleep which depend upon the deferential pressure viscosity of the liquid & of course the workman-ship. the pumps are capable of handling any viscosity. the sleep reduced with viscosity but the viscosity power increases. the pump has sed priming capability however some net positive to avoid cavitation depending upon the viscosity of the liquid to be pumped & the pump speed