Considerations for Backflow Prevention Device Assemblies

Clearances – Backflow prevention device assemblies shall be installed to prevent flooding and mechanical damage with adequate space to facilitate maintenance and testing.

The installation should not require platforms, ladders, or lifts for access.

Adequate clearances from floors, ceilings, and walls must be provided to access the test cocks and to allow the repair and/or removal of the relief valve and check valves.

Drainage – When installing backflow prevention device assemblies, drainage shall be provided to accommodate discharge during testing or draining of the unit and for relief valve discharges. Drainage capacity shall be sized to accommodate both intermittent discharges and catastrophic failures.

Pit Installations – Backflow prevention devices assemblies shall not be installed in pits due to considerations for access, safety, and gravity drainage.

Above Grade Installations– Protective Enclosures – Backflow prevention device assemblies shall be installed above grade to provide gravity drainage and to improved access for servicing, testing, and enhanced safety.

Installation within a Building – Mechanical rooms or area within the building where backflow prevention device assemblies are located shall be heated where necessary to prevent freezing and have adequate lighting. Access and drainage must be considered when installing backflow prevention device assemblies in buildings. The property owner must be made aware of the potential for water damage in the event of a catastrophic discharge of the backflow prevention device assembly.

Backflow prevention device assemblies shall not be installed next to electrical panels and areas of excessive heat shall be avoided.

Supports – All backflow prevention device assemblies shall be adequately supported and/or restrained to prevent lateral movement. Pipe hangers, braces, saddles, stanchions, piers, etc., should be used to support the device and should be placed in a manner that will not obstruct the function of or access to the backflow prevention device assembly.

Strainers – The quality of the supply water shall be considered and strainers are recommended prior to each backflow prevention assembly on non-firefighting water lines where the water quality is questionable and causes fouling of the check valves. Strainer on fire service lines are not to be used without the approval of the authority having jurisdiction. Do not install a strainer ahead of the backflow preventer on seldom used, emergency water lines (i.e. fire sprinkler lines). The strainer mesh could potentially become clogged with debris present in the water and cause water blockage during an emergency.

Hydraulically Sized – The backflow prevention device assembly shall be sized hydraulically, taking into account both the volume of water required and the pressure loss of the backflow prevention device assembly.

Temperature – Backflow prevention device assemblies shall be protected from freezing temperatures and if installed where water temperatures will reach 100 degrees F or above, a hot water type assembly must be used.

Water Hammer – Water hammer downstream of the backflow prevention device assembly can create excessive pressure on the downstream check valve. To avoid possible damage to the system and backflow prevention device assemblies, water hammer arresters, surge protectors, soft seated check valves or expansion tanks shall be used where necessary.

Configuration – All assemblies shall be installed horizontally unless they are specifically approved for vertical installation.

Interruption in Water Service – Parallel installations should be considered at those facilities where water service cannot be interrupted.

Hazardous Areas – Backflow prevention device assemblies shall not be installed in areas containing corrosive, toxic or poisonous fumes or gases that could render the assembly inoperable or pose a safety hazard to personnel.