A self-sealing waste valve uses a flexible silicone or elastomeric membrane in place of a conventional water seal to prevent drain odours entering the room. After each discharge the membrane closes automatically against the outlet, providing a dry seal that is unaffected by evaporation or siphonage. UK installations should be in line with BS EN 274 and Building Regulations Part H1, and the valve must be installed the correct way up with adequate access for replacement. Self-sealing valves are commonly used in concealed locations such as under shower trays, in vanity units and in loft conversions where venting routes are limited. They offer an alternative to anti-siphon traps in long branch runs. The membrane is a wearing part and may need replacement after several years of service.
Self-sealing waste valve
Membrane valve replacing a traditional trap by sealing automatically after each discharge.
