Question 1

A Double Check Valve assembly contains how many check valves?

Accepted Answer

A Double Check assembly has exactly two check valves in series. These two valves provide protection against both backpressure and backsiphonage by preventing water flow in the reverse direction.

Question 2

How many test cocks does a Reduced Pressure Zone (RPZ) assembly have?

Accepted Answer

An RPZ assembly has four test cocks: #1 upstream of the assembly, #2 between shutoff and Check #1, #3 in the relief zone (between checks), and #4 downstream of Check #2.

Question 3

What is the primary function of a check valve in a backflow prevention assembly?

Accepted Answer

Check valves contain a moving disc or flapper that seats against the valve body. Forward flow pushes the disc open; reverse flow causes it to seat, preventing backward water flow.

Question 4

Which assembly component is unique to the RPZ and absent in a Double Check assembly?

Accepted Answer

The relief valve is found only in RPZ assemblies. It maintains the zone between the check valves at a pressure lower than inlet and vents excess pressure to prevent zone failure.

Question 5

What does a Pressure Vacuum Breaker (PVB) protect against?

Accepted Answer

A PVB has one check valve and an air inlet valve. The air inlet opens during backsiphonage to admit air and break the siphon. It does not protect against backpressure.

Question 6

What is the primary difference between a PVB and an SVB (Spill-Resistant Vacuum Breaker)?

Accepted Answer

An SVB includes a spill-resistant design element such as a containment pan or internal geometry to prevent water spillage if the air inlet operates indoors. The PVB is designed for outdoor or below-rim applications where spillage is acceptable.

Question 7

How many shutoff valves are found in a standard backflow prevention assembly?

Accepted Answer

A standard assembly has two shutoff valves: one upstream (before the assembly) and one downstream (after the assembly). These allow isolation of the assembly for testing and service.

Question 8

What is the function of the relief valve in an RPZ assembly?

Accepted Answer

The RPZ relief valve opens when zone pressure approaches inlet pressure, venting the zone to prevent Check #2 failure. This maintains zone integrity and is critical to RPZ protection.

Question 9

What are the internal components of a check valve?

Accepted Answer

A check valve contains a disc (or poppet) that moves on a guide, seats against the valve seat, and is actuated by a spring. Forward pressure opens it; reverse flow seats the disc.

Question 10

What indicates a failing internal component in a check valve if the valve cannot pass the required PSID differential test?

Accepted Answer

A failing PSID test can result from any internal damage: a warped or fouled disc, a broken spring, or a damaged seat that prevents sealing. The specific cause requires disassembly.

Question 11

How does Check Valve #1 differ from Check Valve #2 in an RPZ assembly?

Accepted Answer

Check #1 is the inlet check with higher cracking pressure (≥5.0 PSID minimum in RPZ) to prevent dangerous backpressure. Check #2 is the outlet check with lower minimum (≥1.0 PSID) to prevent backsiphonage.

Question 12

What is the function of the air inlet valve in a Pressure Vacuum Breaker?

Accepted Answer

The air inlet opens when the pressure in the downstream line drops below atmospheric during a backsiphonage event. This admission of air breaks the siphon and prevents contamination of the supply.

Question 13

What material is typically used for the disc in a check valve?

Accepted Answer

Check valve discs are typically made from brass or bronze materials that resist corrosion and wear, maintaining proper seating and durability in water service.

Question 14

How many check valves does a Reduced Pressure Zone assembly contain?

Accepted Answer

An RPZ assembly has two check valves (Check #1 inlet and Check #2 outlet) plus a relief valve. The two checks and relief valve work together to provide the highest level of backflow protection.

Question 15

What is the purpose of test cock #3 in an RPZ assembly?

Accepted Answer

Test cock #3 is located between Check #1 and Check #2 in the protected zone. It allows testing of Check #1 and observation of zone pressure. It is also used during relief valve testing.

Question 16

What is the typical size range for residential backflow prevention assemblies?

Accepted Answer

Residential backflow assemblies are typically 3/4 inch to 1.5 inches in diameter to match common residential water service connections and supply demand.

Question 17

Which assembly type is required for protection against both backpressure and backsiphonage?

Accepted Answer

Only the RPZ assembly provides full protection against both backpressure and backsiphonage due to its relief valve design. It is the highest level of protection available.

Question 18

What does the spring in a check valve accomplish?

Accepted Answer

The spring provides a return force that seats the check valve disc when forward pressure is removed. This ensures the valve closes during backsiphonage or backpressure.

Question 19

What is a characteristic difference between assembly types regarding relief valves?

Accepted Answer

Relief valves are found only in RPZ assemblies. Double Check assemblies have no relief mechanism. Vacuum breakers use air inlets instead of relief valves.

Question 20

How is a Spill-Resistant Vacuum Breaker (SVB) distinguished from a standard PVB in visual identification?

Accepted Answer

SVBs incorporate design features like containment pans or specially shaped internal passages to prevent water discharge from the air inlet during normal operation. A PVB has no such protection.

Question 21

What is the function of the valve seat in a check valve?

Accepted Answer

The valve seat is the static sealing surface against which the movable disc seats. A smooth, undamaged seat is essential for the check valve to seal properly and prevent reverse flow.

Question 22

When a Double Check assembly fails to maintain minimum PSID, which internal component is most commonly at fault?

Accepted Answer

A failed PSID reading typically indicates the check valve disc is not seating properly, often due to particle contamination, debris, or disc/seat damage. Water is bypassing the valve.

Question 23

What is the purpose of shutoff valve #1 in a backflow assembly?

Accepted Answer

Shutoff valve #1, located upstream of the assembly, allows the entire assembly to be isolated from the water supply for testing, maintenance, or removal.

Question 24

How many test cocks does a Double Check Valve assembly have?

Accepted Answer

A Double Check assembly has four test cocks: #1 upstream, #2 between shutoff and Check #1, #3 between Check #1 and Check #2, and #4 downstream of Check #2.

Question 25

What distinguishes a double check valve assembly from a reduced pressure zone assembly in terms of backflow protection capability?

Accepted Answer

The RPZ provides superior protection because the relief valve maintains the zone at a pressure below inlet pressure and vents dangerous backpressure. A Double Check relies on both check valves to function; one failure compromises protection.

Question 26

What is the location of test cock #4 in a Double Check assembly?

Accepted Answer

Test cock #4 is located downstream of Check Valve #2 and allows measurement of outlet pressure and testing of Check Valve #2's ability to prevent backsiphonage.

Question 27

How does a PVB assembly protect against backsiphonage when no water is flowing?

Accepted Answer

A PVB's air inlet opens when downstream pressure drops (backsiphonage condition), admitting air to break the siphon. The air inlet is the key to PVB protection during no-flow backsiphonage.

Question 28

What is inside the relief valve of an RPZ assembly?

Accepted Answer

An RPZ relief valve is a spring-loaded poppet valve. The poppet seats against the relief seat, and a spring maintains the cracking pressure. An adjustment screw allows field adjustment of crack pressure.

Question 29

What are the typical materials used in backflow prevention assemblies to resist corrosion?

Accepted Answer

Brass, bronze, and stainless steel are chosen for their corrosion resistance in water applications. These materials maintain dimensional accuracy and prevent sealing surface degradation.

Question 30

What identifies a reduced pressure zone assembly as different from a double check in appearance?

Accepted Answer

The RPZ's relief valve is a visually distinct external component on the assembly body with a vent or drain port. A Double Check has no relief valve and lacks this feature.

Question 31

What is the function of shutoff valve #2 in a backflow assembly?

Accepted Answer

Shutoff valve #2, located downstream of the assembly, allows isolation of the protected zone. It is used to separate the assembly for testing without shutting off the entire supply.

Question 32

Which type of backflow assembly would be appropriate for indoor, below-rim installation in a kitchen faucet?

Accepted Answer

An SVB is designed for indoor, below-rim installations. Its spill-resistant design prevents water from leaking into the sink if the air inlet operates. A standard PVB is not suitable for indoor locations.

Question 33

What is the purpose of Check Valve #2 in both DC and RPZ assemblies?

Accepted Answer

Check Valve #2, the outlet check, is the final barrier against backsiphonage. It prevents water from flowing backward out of the protected zone when downstream pressure drops below system pressure.

Question 34

What indicates that a check valve spring has become weakened or broken?

Accepted Answer

A weakened or broken spring reduces the seating force on the disc. The valve cannot hold the minimum PSID differential because pressure bleeds past the disc. The test fails.

Question 35

How does an air inlet valve in a PVB differ from a relief valve in an RPZ?

Accepted Answer

A PVB air inlet is a check-type valve that opens to admit air and break a siphon. An RPZ relief valve opens to vent pressurized water and maintain zone integrity under backpressure conditions.

Question 36

What is a characteristic of the disc geometry in a reduced cracking pressure check valve versus a high cracking pressure check valve?

Accepted Answer

Check valve disc design directly affects cracking pressure. Lighter discs and weaker springs produce low cracking pressure (≥1.0 PSID). Heavier discs and stiffer springs create high cracking pressure (≥5.0 PSID for RPZ Check #1).

Question 37

What visual sign indicates that an RPZ relief valve may be stuck open or not seating properly?

Accepted Answer

A relief valve that does not seat properly after opening will continuously discharge water from its vent port. This is a clear indication of relief valve failure and assembly malfunction.

Question 38

How many shutoff valve positions exist in a typical residential backflow assembly installation?

Accepted Answer

Standard installations have two shutoff valves: one upstream (before the assembly) and one downstream (after the assembly). Some commercial installations may have additional zone shutoffs.

Question 39

What is the purpose of the relief valve vent or drain opening on an RPZ assembly body?

Accepted Answer

The relief vent allows water vented by the relief valve to discharge safely to atmosphere or drain. This prevents pressure from building in the protected zone during backpressure events.

Question 40

Which assembly component is most frequently contaminated by suspended particles in water, leading to test failures?

Accepted Answer

Check valve seating surfaces (discs and seats) are most susceptible to contamination from suspended particles, debris, or biofilm. These deposits prevent proper sealing and cause test failures.

Question 41

What makes a Reduced Pressure Zone assembly superior to a Double Check for backpressure protection?

Accepted Answer

The RPZ relief valve actively maintains the protected zone at a pressure lower than inlet. If inlet pressure exceeds this, the relief opens and vents water, protecting against dangerous backpressure.

Question 42

What does the guide pin in a check valve accomplish?

Accepted Answer

The guide pin (or stem) constrains the disc to move vertically and prevents lateral binding or jamming. It is essential for smooth valve operation and reliable seating.

Question 43

What is the typical cracking pressure (minimum opening pressure) for the relief valve in an RPZ assembly?

Accepted Answer

The RPZ relief valve must have a minimum cracking pressure of 2.0 PSID. This ensures the zone pressure remains protected but allows the relief to open when dangerous backpressure is detected.

Question 44

How does contamination in Check Valve #1 of an RPZ compare in significance to contamination in Check Valve #2?

Accepted Answer

Check Valve #1 contamination is more critical because it protects against backpressure. If Check #1 fails, the relief valve cannot maintain zone integrity. Check #2 failure affects backsiphonage protection only.

Question 45

What is the relationship between assembly size and PSID minimum requirements?

Accepted Answer

PSID minimum requirements are the same regardless of assembly size. A 3/4-inch DC must maintain 1.0 PSID per check valve, the same as a 2-inch DC assembly.

Assembly Components Practice Questions

Download VoltExam — $17.99 Lifetime

More Backflow Prevention Certification Exam Topics