A closed system for harvesting fat through liposuction, concentrating the aspirate so obtained, and then re-injecting the concentrated fat into a patient comprises as its main components a low pressure cannula having between about 7 to 12 side holes of about 1-2 mm by 2.0 to 4.0 mm, a spring loaded syringe holder with a constant force or coiled ribbon spring to apply a substantially constant pressure over the full excursion of the plunger, and a preferably flexible collection bag which is also preferably graduated, cylindrical over most of its body and funnel shaped at its bottom, all of which are connected through flexible tubings to a multi-port valve. The multi-port valve has two flutter/duck bill valves which restrict the fluid flow to a one way direction which effectively allows the syringe to be used to pump fat out of a patient and into a collection bag in a continuous manner. After the bags are centrifuged to concentrate the fat, the excess fluids are separated and the valve is re-connected to permit the syringe pump to reverse fluid flow to graft the concentrated fat back into the patient.