A Double Check valve protects this Garden Tap. The double check valve meets Local Water Regulations as detailed in Southern Water, Water Supply (Water Fittings) Regulations 1999 "Schedule 2.6.15.20 Taps to which hoses are, or maybe, connected and located in house garden locations are to be protected against backflow by means of a double check valve." A double-check valve is not the same as products sold with a check valve which does not meet Water Regulations UK Made for FixTheBog