Trigger pumps

A trigger pump dispenser comprising a main body which comprises a conical pump chamber, the main body includes an inlet port and an outlet port that are in communication with the pump chamber, the dispenser comprises a piston, seated in the pump chamber, for defining a variable volume in said pump chamber and movable between a retracted position of larger chamber volume and an inserted position of lesser chamber volume, the pump chamber comprises a venting hole, an inlet valve is seated between the pump chamber and the inlet port, the inlet valve is adapted to open the inlet port when liquid to be dispensed is drawn into the pump chamber through the inlet port as the pump chamber volume increases when the piston is moved from the inserted position to the retracted position, an outlet valve is seated between the pump chamber and the outlet port, the outlet valve is adapted to open the outlet port when the pump chamber decreases in volume as liquid therein is dispensed through the outlet port and adapted to close when the pump chamber increases in volume.