The system for opening and/or closing an inlet valve (10) and/or an outlet valve (30) of a liquid container (24), particularly for water toilets, water tanks or the like, comprises an inlet tube (16) with an inlet valve (10) in the upper portion of the container (24) and an outlet tube (20) with an outlet valve (30) in the bottom portion (25) of the container (24), both valves (10, 30) being provided with a valve body. It is characterized by the use of a bistabile inlet valve (10) having a lag-free opening and closing characteristic without any intermediate opening position of the valve body (14; 38, 46), the closing stroke of the valve body being assisted by the flow of the liquid.