Water separator for continuous separation of water, air and particles, said separator comprising an inlet pipe (18) for receipt of a mixture of water, air and particles simultaneously from several sources such as dental surgeons etc. an outlet pipe (22) being connected to a suction motor (23), an upper chamber (2) being connected with a lower chamber (3) by a valve (17) in the bottom of the upper chamber (2), the lower chamber (3) normally being closed by a check valve (8) in the bottom, a three- way valve (24) located in an air connection pipe (20) being adapted to establish a connection between the upper (2) and lower (3) chambers in a first position and closing said connection to the upper chamber and allowing atmospheric air to enter into the lower chamber (3) in a second position, and the upper chamber (2) comprising a coarse filter (4) capturing particles from the liquid flow to the lower chamber (3), where the water separator comprises two tanks, a main tank (1) and a safety tank (11), which are connected through a connection pipe (19) from the upper chamber (2) in the main tank (1) to the safety tank (11) and through the air connection pipe (20) from the lower chamber (3) in the main tank to the safety tank (11), that the inlet pipe (18) is through the lid of the main tank (1), that the outlet pipe (22) is through the lid of the safety tank (11), and the safety tank (11) normally being closed by a check valve (15) in the bottom.
