The invention relates to a gravity operated mechanical flushing apparatus, which is operated without any external power source. A weight sensing element (1) provided with a tank (T) contains a component part (8) able to move along a vertical path against a spring force and a controlled feeder valve (5) coupled to a water supply system. The weight sensing element (1) has at its lower end an output (6) able to move vertically causing a mechanical operating event, said output (6) is coupled to a ratchet mechanism (3) through a coupling transmission (2). The ratchet mechanism (3) is able to transmit every second mechanical operating event presented by said output (6) and said transmission (2) to a control element of said controlled feeder valve (5) by means of a further transmission (4) in order to transmit an activating mechanical movement. The controlled feeder valve (5) is coupled to a pipe (17) for filling a determined amount of water for flush from the water supply system into said tank (T) through an outlet (18) of said pipe (17).