A micropump comprises a valve system having one gasket (10) shaped to define three cavities (12, 12a, 12b) connected respectively to a piston chamber, an inlet port and an outlet port of the pump. A valve switching element (16) having at least one groove (17) is movably mounted on the gasket such that, during piston instrokes, said groove moves along a part of the gasket adjacent to the cavities connected respectively to the piston chamber and the inlet port of the pump, thereby creating a leakage between said cavities so that fluid is sucked into the piston chamber during a piston instroke. During piston outstrokes, said groove moves along a part of the gasket adjacent to the cavities connected respectively to the piston chamber and the outlet port of the pump, thereby creating a leakage between said cavities so that fluid is expelled out of the piston chamber through the outlet port during a piston outstroke.
