Water distribution systems are designed to operate with continuous positive pressure. This helps ensure contamination cannot enter the system through points of connection or leaks. Though difficult to detect, water pressure can sometimes be disrupted causing water to accidentally flow backwards causing a cross connection between building and municipal water systems. This can result in siphoning unknown materials into the drinking water. Other times, pumps or water heating devices in homes and businesses can overcome the water system pressure. In a fire protection system, backflow prevention can be achieved with two one-way valves assembled in a series called a Double Check Valve Assembly (DCVA).   A Reduced Pressure Zone Assembly (RPZA) provides the maximum protection and along with the DCVA is the most common type of backflow prevention used in fire protection systems. This assembly contains two spring-loaded check valves with a differential relief valve between them and two shut off valves and four test cocks. The RPZA operates like a DCVA with the addition of a relief valve, if there is a backflow the check valves will close, and the relief valve will open, resulting in a reduced pressure zone and air gap between the check valves. The two shut off valves and four test cocks allow this assembly to be field tested as well.

 

Inspection Cycles

In most municipalities backflow preventer inspections are required annually.  Specific requirements are determined by the local Cross Connection Control Program.

Common Deficiencies

A deficiency is identified during regular inspections when the devices and components do not meet acceptable standards. Here are a few commonly found deficiencies for backflow devices:

• Expired certification
• Backflow test failure
• Physical damage

Related Services

• Inspection & Maintenance
• Backflow Preventer Installations
• Repairs