Abstract: The invention relates to a pressure valve with a flow passage (3) having a valve body (14) and a lifting plate (21) that has a surface area A2 transversally of the flow passage (3) that exceeds the cross sectional area A1 of the flow passage (3) at the valve seat (13) of the valve body, said pressure valve being configured such that, at any time, the container is in communication with the area above the lifting plate (21). The invention is characterised in that the pressure valve also comprises a magnet (8) and a magnetisable body (9); and that the force of attraction Fm between the magnet (8) and the magnetisable body (9) and the mass of the lifting plate (21) contributes to defining the abutment force Fc, of the valve body (14) against the valve seat (13) in the closed state of the pressure valve.