Backflow Preventers

Drinking water networks can be contaminated when water flows backwards from a connected property or system into the distribution main. This can occur when supply pressure drops during mains burst repairs, fire-fighting operations or peak demand periods, drawing contaminated fluid back through any unprotected cross-connection. Backflow prevention is a statutory requirement in most European jurisdictions and is the subject of EN 1717, the European standard for protection against pollution of potable water in water installations.

EN 1717 defines five fluid risk categories. Category 1 is potable water with no contamination risk. Category 5 covers the most hazardous substances including toxic chemicals, radioactive materials and faecal contamination. The appropriate backflow prevention device is determined by the fluid category risk at the connection point. Installing an insufficient device exposes the water utility and the property owner to liability for any resulting contamination incident.

The reduced pressure zone (RPZ) valve assembly is the highest-level mechanical backflow prevention device and is required for Category 4 and 5 fluid risks. It comprises two independently acting check valves with a middle zone maintained at a pressure lower than the supply pressure by a relief valve. If either check valve fails, the relief valve discharges the middle zone to drain rather than allowing contaminated fluid to pass through the assembly. RPZ assemblies must be installed above flood level with a visible air gap to the drain, and require annual testing and certification by a trained engineer.

Double check valve assemblies are suitable for Category 2 and 3 fluid risks. Two independently acting check valves in series provide protection against backflow without the pressure loss and drainage requirement of an RPZ. Double check assemblies are widely used for connection points on commercial properties, irrigation systems, car wash facilities and building heating systems.

All backflow prevention assemblies in our range are WRAS approved for use in the UK and Ireland and comply with EN 1717. Size range is DN15 to DN250 with flanged or threaded connections. Test reports and compliance documentation are included with every supply.

Selection of the correct device requires knowledge of the fluid risk category at the connection point, the operating pressure range and the flow rate. AFC Valves Europe can advise on device selection for new connections and can assist contractors in preparing backflow prevention schemes for water utility approval.