Buffalo 4 inch / 110mm Non Return Valve, stainless steel door anti rodent valveBuffalo Retro fit Non Return Valve product description: 110mm Buffalo Stainless Steel Door Non Return valve with WRc Approval. Suitable for clay, PVC & cast iron pipe systems to suit installation within either an outlet or inlet of a drainage chamber. Secured into pipework within drainage chambers effectively discouraging rats and rodents from entering a property via a drainage system. Non return valve product features Stops backflow of effluent into