Abstract: The filling systems according to the invention utilize pneumatic pressure maintained within closely held tolerance limits to impose a constant dispensing force upon the material being dispensed. The invention in one embodiment utilizes a buffer tank system in which the product to be dispensed is transferred from a supply tank (11) to the buffer tank (12) where the desired pressure is induced through a pneumatic head which is introduced above the product level. The product level in the buffer tank (12) is allowed to fluctuate within a relatively narrow band of depth so as to negate the effect of changes in gravity head pressure. The closed and pressurized system is refilled by forcing the incoming product into the tank (12) under a higher pressure than that in the buffer tank (12). The air within the tank (12) that is displaced as a result of introducing the new product is automatically vented to atmosphere through a precision regulation system (45).