Buffalo Pest Control Water and Rodent Non Return Valve 110mm / 4 inchDRAIN AND SEWER NON RETURN VALVE to stop rats and rodents from climbing up drain pipes, sewers, toilets and into your home. ANTI RODENT FLAP VALVE with stainless steel flap and face prevents rodents from entering the property. The flap allows rats to leave the property but prevents them from coming back up the sewer or drain pipe. When fully inserted, the a complete stainless steel face prevents the rats from entering your property and protecting your