HepVo Waste Non-Return Valve 32mmStop unpleasant odours escaping into your living space with the HepVo Waste Non Return Valve 32mm. The hygienic self sealing waste valve is made for closing your waste connection below a sanitary appliance. It aims to reduce negative pressure within the waste system as it opens and brings in fresh air until a pressure equilibrium is reached. The valve is efficient without impacting performance and risking foul air escaping from the drain or sewer.