Honeywell BSP Pipe fittings UK The Power of Connected Backflow Preventer Backflow preventer are suitable for the protection of drinking water, and potable water systems. Protection against back pressure, back flow and back syphonage. Fluids up to and including liquid cat 3 to EN 1717 are protected.   Technical Specs Liquid category (EN1717)class 3 DN size:  [...]