CIT - Certified Irrigation Technician Backflow Prevention Devices 2 — Questions and Answers

Question 1: A technician discovers that an RPZ assembly's relief valve is continuously discharging water. What is the most likely cause of this condition?

The supply pressure is too high
The first check valve is fouled or not seating properly (Correct answer)
The downstream shutoff valve is closed
The test cocks are open

Correct answer: The first check valve is fouled or not seating properly

When the first check valve of an RPZ assembly fails to seat properly, the zone of reduced pressure cannot be maintained. The relief valve opens to discharge water and prevent backflow, indicating that the first check valve needs repair or replacement.

In an RPZ assembly, the first check valve maintains higher pressure on the supply side. If it becomes fouled or fails to seat, the pressure in the zone between check valves rises to match supply pressure. The relief valve is designed to open when this differential is lost, as a safety measure to prevent backflow. Continuous discharge signals first check valve failure and the assembly must be taken offline for repair.

Question 2: According to most plumbing codes, how often must a testable backflow prevention assembly be tested after installation?

Every 6 months
Annually (Correct answer)
Every 2 years
Only when there is a suspected failure

Correct answer: Annually

Most plumbing codes and water purveyors require that testable backflow prevention assemblies (RPZ, DCVA, PVB, SVB) be tested at least annually by a certified tester. Some jurisdictions may require more frequent testing.

Annual testing is the standard requirement across most jurisdictions in the United States. The purpose is to verify that all internal components — check valves, relief valves, and air inlet valves — are functioning properly. Testing must be performed by a certified backflow assembly tester, and results are typically reported to the local water purveyor. Some high-hazard installations may require semi-annual testing.

Question 3: Which backflow prevention device relies on an air gap between the outlet and the flood rim of a receiving vessel?

Reduced Pressure Zone Assembly
Atmospheric Vacuum Breaker
Air Gap Separation (Correct answer)
Double Check Valve Assembly

Correct answer: Air Gap Separation

An air gap separation is the simplest and most reliable form of backflow prevention. It creates a physical disconnect between the water supply outlet and the flood rim of a receiving vessel, making backflow physically impossible.

An air gap is defined as the unobstructed vertical distance between the lowest point of a water supply outlet and the flood level rim of the receiving vessel. The minimum air gap is typically two times the diameter of the supply pipe, but never less than one inch. While it provides the highest level of protection, it is impractical for most irrigation systems because it requires the water to discharge into an open vessel before being re-pressurized.

Question 4: A Pressure Vacuum Breaker (PVB) must be installed at what minimum height above the highest downstream outlet?

6 inches
12 inches (Correct answer)
18 inches
24 inches

Correct answer: 12 inches

A PVB must be installed at least 12 inches above the highest downstream point of use (sprinkler head or emitter). This ensures that backpressure cannot develop and the air inlet valve can function properly.

The 12-inch minimum installation height above the highest downstream outlet is critical because PVBs protect only against backsiphonage, not backpressure. If a PVB were installed below the highest downstream point, static head pressure from elevated piping could create backpressure, which the PVB cannot handle. In hilly terrain, this requirement may make PVBs impractical, necessitating an RPZ or DCVA instead.

Question 5: During a backflow assembly test, the technician finds that the second check valve on a Double Check Valve Assembly (DCVA) has zero differential. What action should be taken?

The assembly passes the test since the first check holds
Clean and repair or replace the second check valve components (Correct answer)
Replace the entire assembly immediately
Increase the supply pressure to compensate

Correct answer: Clean and repair or replace the second check valve components

A zero differential on the second check valve means it is not functioning properly and must be repaired or have its internal components replaced. Both check valves must maintain a minimum pressure differential for the assembly to pass the test.

In a DCVA, both check valves must independently hold a minimum pressure differential (typically 1 PSI for the second check). A zero reading means the disc, seat, or spring has failed and water can flow backward through that check. Simply relying on the first check is not acceptable — both must function independently. The technician should disassemble the second check, inspect the rubber disc and seat for wear or debris, and replace components as needed before retesting.

Question 6: Which type of backflow condition occurs when a water main breaks or a fire hydrant is opened, creating a negative pressure in the supply line?

Backpressure
Backsiphonage (Correct answer)
Water hammer
Pressure surge

Correct answer: Backsiphonage

Backsiphonage occurs when negative pressure or a vacuum develops in the supply piping, such as when a water main breaks or a nearby fire hydrant is opened. This can siphon non-potable water from an irrigation system back into the public water supply.

Backsiphonage is fundamentally different from backpressure. While backpressure involves the downstream pressure exceeding supply pressure (pushing water back), backsiphonage involves negative pressure on the supply side pulling water back through a siphon effect. Common causes include water main breaks, firefighting operations, and flushing of water mains. All backflow prevention devices protect against backsiphonage, but only RPZs and DCVAs protect against both backsiphonage and backpressure.

CIT - Certified Irrigation Technician Backflow Prevention Devices 2

A technician discovers that an RPZ assembly's relief valve is continuously discharging water.
What is the most likely cause of this condition?