Reflux valve means

A reflux valve means for installation in a fluid conduit that has a fluid outflow end, wherein said valve means includes a vacuum valve intended for connection to a conduit branch substantially near a top part of the conduit upstream of its outlet end, said valve including a valve housing having a passageway which establishes communication between atmosphere surrounding the valve and the conduit branch, said passageway having a valve seat and a valve plate which can be moved into and out of sealing contact with said seat under the influence of a pressure which is higher and lower, respectively, in said conduit than atmospheric pressure, said valve plate of said vacuum valve being constructed for elastic deformation forward and away from a generally cupped shape in the closed state of the valve under the influence of pressure variations that normally occur in a fluid conducted in said conduit branch, said valve plate being provided on a surface thereof that lies proximal to the branch conduit with radial grooves which define flexing or bending regions for facilitating deformation of said valve plate into and out of said cupped-shape.