The invention relates to a sealing gasket (4) used in water heating systems (A) in which domestic water is heated via pressure type vacuum tube (2) solar energy and ensuring sealing at the connection between the vacuum tubes (2) and the hot water boiler (1), comprising a pressure screen (4.1) enabling the sealing gasket (4) to exert extra pressure on inner surface of the hot water boiler (1) and the vacuum tube (2) with the impact of the pressure in the hot water boiler (1) and a conical surface (4.2) ensuring extra compression of the sealing gasket (4) between the hot water boiler (1) and the vacuum tube (2) together with the increasing pressure.