Gardena Back Flow Preventer 23mm (5/8"), 26.5mm (3/4") - Gardena 9951-28 Ref: GRD9951-28 Prevents water returning to the mains when it has been in the hose pipe. This is a legal requirement when using outdoor hoses as the water can sit in the hose and become contaminated List price £19.99 Grovelands Online price including Nextday Delivery £17.99 Price: £17.99 (Including VAT at 17.5%)