Non-return device

A non-return device for use between a waste outlet and a waste pipe in a plumbing system;

• the device comprising:
• a tubular housing, for connection between the waste outlet and the waste pipe;
• flexible, impervious wall members disposed within the housing for communication with the waste outlet at a first, upstream, end of the housing, the flexible, impervious wall members being of complementary shapes disposed face-to-face in surface contact, so that there is no through passage between them in a normal state and resiliently urged into the normal state;
• support means comprising an annular sleeve having a first part located coaxially within said housing at an axial inlet end thereof, and a second part projecting axially from said housing and comprising a radial flange, the first part of said annular sleeve being arranged to hold said wall members spaced apart from one another at the first end thereof to define an inlet for fluid, thereby enabling it to reach the interface of said members, whereby in-flowing fluid can force said members apart to permit flow between them from the waste outlet and to the other end of the device, whereas flow in the opposite direction is prevented by the close surface contact between the members;
• and
• a nut for mounting the device upon the waste outlet, said nut comprising an annular recess, which recess surrounds the second part of the annular sleeve and receives the flange therein in such a manner as to permit axial movement thereof within the recess;
• wherein the arrangement is such that mounting of the nut upon the waste outlet causes axial movement of the flange within the annular recess, so as to compress a portion of the wall members situated in a region adjacent the inlet against the support means and also compress the portion of the wall members against the housing and thereby effect a seal between the support means and the housing.