Anti-vacuum valve
An anti-vacuum valve is placed at the highest point of the vertical sewer branch and serves to suck in air when the cistern is released on the toilet bowl, so that the water from the cistern instead of creating a vacuum sucks air through the anti-vacuum valve and thus odors do not enter in the entire building and especially on the first floors, where the water closures of the floor siphons and the siphons of the toilet sinks can be drained, if there is no anti-vacuum valve installed, then conditions are created for the formation of a vacuum and suction of water when running cisterns with a large water content resulting in foul odors entering.