CIT - Certified Irrigation Technician Certified Irrigation Technician Backflow Prevention Devices 1 — Questions and Answers
Question 1: Which type of backflow prevention assembly uses two independent check valves and a differential pressure relief valve between them?
- Double Check Valve Assembly (DCVA)
- Reduced Pressure Zone Assembly (RPZ) (Correct answer)
- Pressure Vacuum Breaker (PVB)
- Atmospheric Vacuum Breaker (AVB)
Correct answer: Reduced Pressure Zone Assembly (RPZ)
The Reduced Pressure Zone (RPZ) assembly contains two independently operating spring-loaded check valves with a differential pressure relief valve in the zone between them. This relief valve opens to atmosphere if the pressure in that zone rises, providing the highest level of backflow protection for high-hazard applications.
Question 2: An Atmospheric Vacuum Breaker (AVB) must NOT be installed in which of the following conditions?
- On a system with static pressure below 60 psi
- Where the device will be subject to continuous pressure for more than 12 hours (Correct answer)
- Upstream of a zone control valve
- On a residential drip irrigation system
Correct answer: Where the device will be subject to continuous pressure for more than 12 hours
An AVB is not designed to remain under continuous supply pressure. When subjected to pressure for more than 12 continuous hours, the internal float or poppet can become seated and fail to open when backpressure or backsiphonage occurs, defeating the device's purpose. It must be installed in systems that cycle off regularly.
Question 3: When testing a Double Check Valve Assembly (DCVA), a tester finds that Check Valve #1 reads 2.0 psi and Check Valve #2 reads 1.0 psi. What is the correct assessment?
- Both checks pass; the assembly is in good working order (Correct answer)
- Check Valve #1 fails because it must hold at least 3.0 psi
- Check Valve #2 fails because it must hold at least 1.0 psi
- Both checks fail because the minimum hold for a DCVA check valve is 1.0 psi, and both must exceed it
Correct answer: Both checks pass; the assembly is in good working order
For a DCVA, each check valve must hold a minimum differential pressure of 1.0 psi. Check Valve #1 at 2.0 psi and Check Valve #2 at 1.0 psi both meet or exceed this threshold, so the assembly passes inspection. A reading of exactly 1.0 psi is acceptable — failure occurs only below 1.0 psi.
Question 4: A backflow preventer installed on an irrigation system serving a property with a fertilizer injector (chemigation) would BEST be protected by which assembly?
- Atmospheric Vacuum Breaker (AVB)
- Pressure Vacuum Breaker (PVB)
- Double Check Valve Assembly (DCVA)
- Reduced Pressure Zone Assembly (RPZ) (Correct answer)
Correct answer: Reduced Pressure Zone Assembly (RPZ)
Chemical injection (chemigation) introduces a severe health hazard into the irrigation water. Chemicals entering the potable supply could be life-threatening, classifying this as a high-hazard cross-connection. Only an RPZ assembly provides the level of protection required for high-hazard applications because its differential relief valve actively discharges to atmosphere if either check valve fails.
Question 5: Where must the air gap distance between the supply pipe outlet and the flood level rim of a receiving vessel be set, at minimum, according to standard plumbing code?
- Equal to the pipe diameter
- Twice the internal diameter of the supply pipe, but not less than 1 inch (Correct answer)
- Three times the internal diameter of the supply pipe
- 1/2 inch regardless of pipe size
Correct answer: Twice the internal diameter of the supply pipe, but not less than 1 inch
Standard plumbing codes specify that an air gap must be at least twice the internal diameter of the supply pipe, with an absolute minimum of 1 inch. This ensures that even under the worst flooding conditions, the flood rim cannot reach the supply outlet, maintaining a true physical separation between the potable water supply and the receiving vessel.
Question 6: A technician is replacing a failed backflow preventer on an irrigation system and discovers the old device was installed below grade in a vault. Which of the following is the most important concern regarding the replacement installation?
- The replacement device must be a PVB to comply with underground installation requirements
- Submerged or flooded vaults can expose the device to backpressure conditions that require an RPZ-rated assembly (Correct answer)
- Underground installation automatically voids any manufacturer warranty
- Only AVBs are approved for below-grade installation in most jurisdictions
Correct answer: Submerged or flooded vaults can expose the device to backpressure conditions that require an RPZ-rated assembly
Backflow preventers installed in below-grade vaults are at risk of submersion if the vault floods. A submerged assembly can be exposed to back-pressure from surrounding water or contaminated vault water entering the relief valve of a standard device. For this reason, many codes require an RPZ or specific vault drainage provisions, and the installer must assess flood risk when choosing the appropriate assembly for a below-grade location.
CIT - Certified Irrigation Technician Certified Irrigation Technician Backflow Prevention Devices 1
Which type of backflow prevention assembly uses two independent check valves and a differential pressure relief valve between them?