Master / Journeyman Plumber Exam
Backflow Prevention Practice Questions
30 practice questions with detailed explanations — aligned to the Master / Journeyman Plumber Exam.
Q1.What is the minimum air gap required between the supply outlet and the flood level rim of a fixture?
A.1 inchB.Twice the diameter of the supply pipeC.Three times the diameter of the supply pipeD.6 inchesB. Twice the diameter of the supply pipeExplanation: IPC 608.15.1 requires the air gap to be at least twice the diameter of the effective opening of the supply pipe, but never less than 1 inch.
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Q2.Which backflow preventer provides the highest level of protection against high-hazard contamination?
A.Double Check Valve Assembly (DCVA)B.Pressure Vacuum Breaker (PVB)C.Reduced Pressure Zone Assembly (RPZ)D.Atmospheric Vacuum Breaker (AVB)C. Reduced Pressure Zone Assembly (RPZ)Explanation: The RPZ (Reduced Pressure Principle Backflow Preventer) protects against both backpressure and backsiphonage for high-hazard (health hazard) applications.
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Q3.An Atmospheric Vacuum Breaker (AVB) shall NOT be installed where:
A.It is subject to continuous pressure for more than 12 hoursB.It is installed 6 inches above the flood rimC.It protects a hose bibbD.It is used for a sink sprayerA. It is subject to continuous pressure for more than 12 hoursExplanation: AVBs are not designed for continuous pressure (pressure applied for more than 12 hours in a 24-hour period) because the air inlet valve may stick closed.
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Q4.A Pressure Vacuum Breaker (PVB) must be installed at least ___ inches above the highest downstream piping or outlet.
A.6B.12C.18D.24B. 12Explanation: IPC 608.13.5 requires PVBs to be installed a minimum of 12 inches above the highest downstream usage to function correctly.
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Q5.Which device is approved for protecting against backpressure?
A.Atmospheric Vacuum BreakerB.Pressure Vacuum BreakerC.Double Check Valve AssemblyD.Hose connection vacuum breakerC. Double Check Valve AssemblyExplanation: Vacuum breakers (AVB, PVB) only protect against backsiphonage. Double checks (DCVA) and RPZs protect against backpressure and backsiphonage.
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Q6.Testable backflow prevention assemblies must be tested:
A.Every 6 monthsB.AnnuallyC.Every 3 yearsD.Only upon installationB. AnnuallyExplanation: IPC 312.10 requires annual testing and inspection of backflow prevention assemblies to ensure they are working properly.
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Q7.A hose bibb vacuum breaker (ASSE 1011) is required on:
A.Water heater drainsB.Sill cocks and hose bibbs where a hose can be attachedC.Shower armsD.Lavatory faucetsB. Sill cocks and hose bibbs where a hose can be attachedExplanation: IPC 608.13.6 (and 608.15.4.2) requires vacuum breakers on hose connections to prevent backsiphonage from hoses left in puddles or chemical buckets.
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Q8.The Double Check Valve Assembly (DCVA) is typically suitable for:
A.High hazard applicationsB.Low hazard (non-health hazard) applicationsC.Chemical injection systemsD.Any applicationB. Low hazard (non-health hazard) applicationsExplanation: DCVAs are approved only for low-hazard applications (pollutants, not contaminants) because they do not have a relief valve to dump water if both checks fail.
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Q9.Backsiphonage is caused by:
A.Pressure in the downstream piping exceeding the supply pressureB.Negative or reduced pressure in the supply pipingC.A pump downstreamD.Heating the waterB. Negative or reduced pressure in the supply pipingExplanation: Backsiphonage occurs when a vacuum (negative pressure) in the supply line sucks contaminated water back into the potable system (e.g., water main break).
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Q10.Carbonated beverage dispensers must be protected by:
A.A vented dual check valve with an atmospheric ventB.A single check valveC.An air gap onlyD.A hose bibb vacuum breakerA. A vented dual check valve with an atmospheric ventExplanation: IPC 608.16.1 requires a backflow preventer for carbonators (ASSE 1022 - vented dual check) to prevent CO2 gas from mixing with copper pipe, which creates toxic copper carbonate.
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Q11.An RPZ assembly shall NOT be installed:
A.In a vertical positionB.In a pit or vault where it could be submergedC.IndoorsD.Above the floorB. In a pit or vault where it could be submergedExplanation: IPC 608.13.2 requires RPZs to be installed where the relief port cannot be submerged. Pits are prohibited because floodwater could enter the potable supply through the open relief port.
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Q12.A barometric loop must rise at least ___ feet above the highest fixture it supplies.
A.10B.25C.35D.50C. 35Explanation: A barometric loop protects against backsiphonage by rising 35 feet, effectively exceeding the atmospheric lift capability of a vacuum.
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Q13.Lawn irrigation systems with chemical injection pumps are considered:
A.Low hazardB.High hazardC.No hazardD.Aesthetic onlyB. High hazardExplanation: Injecting fertilizers or pesticides makes the system High Hazard, requiring an RPZ or PVB (if no backpressure).
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Q14.Which marking on a vacuum breaker indicates the minimum installation height?
A.UPCB.ASSEC.C-L or Critical LevelD.Flow ArrowC. C-L or Critical LevelExplanation: The 'C-L' (Critical Level) mark must be at the required distance (6" or 12") above the flood level rim.
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Q15.A connection between a potable water supply and a non-potable source is defined as a:
A.Cross-connectionB.BypassC.ManifoldD.Fixture branchA. Cross-connectionExplanation: A cross-connection is any physical link between the potable water system and any other substance or non-potable source.
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Q16.Stop-and-waste valves (valves with a drain opening) shall not be installed:
A.Above groundB.UndergroundC.In hot water linesD.In basementsB. UndergroundExplanation: IPC 608.8 prohibits stop-and-waste valves underground because contaminated groundwater can enter the potable system through the drain port when the pressure drops.
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Q17.An Atmospheric Vacuum Breaker (AVB) must be installed at least ___ inches above the flood level rim of the fixture.
A.1B.6C.12D.18B. 6Explanation: IPC 608.13.6 requires AVBs to be at least 6 inches above the flood level rim.
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Q18.Backflow protection for a fire sprinkler system utilizing chemical additives (antifreeze) requires a:
A.Double Check ValveB.Reduced Pressure Zone AssemblyC.Single Check ValveD.Vacuum BreakerB. Reduced Pressure Zone AssemblyExplanation: Chemical additives create a high hazard (toxic), mandating an RPZ. (Systems with water only can often use a DCVA).
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Q19.The relief port of an RPZ must discharge to:
A.A sanitary sewer directlyB.An indirect waste receptor via an air gapC.The floor without a drainD.A bucketB. An indirect waste receptor via an air gapExplanation: The discharge must be visible and connect indirectly (air gap) to the drainage system to prevent sewer backup into the device.
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Q20.Spill-resistant Vacuum Breakers (SVB) are designed for:
A.High backpressureB.Continuous pressure applications where spillage is undesirable (indoor use)C.Underground useD.Toxic chemicals onlyB. Continuous pressure applications where spillage is undesirable (indoor use)Explanation: SVBs (ASSE 1056) reduce water spillage upon startup and are rated for continuous pressure, unlike AVBs.
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Q21.Which of the following is considered a 'Low Hazard' (Pollution)?
A.SewageB.Food coloring or nontoxic dyeC.Chemical fertilizerD.Radioactive materialB. Food coloring or nontoxic dyeExplanation: Low hazard substances are objectionable but not dangerous to health (e.g., food products).
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Q22.A potable water connection to a residential boiler (without chemicals) is typically protected by a:
A.Dual check valve with intermediate atmospheric vent (ASSE 1012)B.Single check valveC.Vacuum breakerD.Air gapA. Dual check valve with intermediate atmospheric vent (ASSE 1012)Explanation: ASSE 1012 devices are standard for residential boiler feed lines where no chemicals are used.
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Q23.Where non-potable water is used for flushing toilets (gray water), the piping must be:
A.CopperB.Painted purple or marked 'Non-potable water'C.White PVCD.GalvanizedB. Painted purple or marked 'Non-potable water'Explanation: IPC 608.9 requires non-potable water systems to be identified by purple pipe or purple tags/tape to prevent cross-connection.
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Q24.Backpressure backflow can be caused by:
A.A broken water mainB.High water demand from fire fightingC.Boiler pressure exceeding supply pressureD.Draining the systemC. Boiler pressure exceeding supply pressureExplanation: Backpressure happens when the downstream pressure is higher than the supply pressure (e.g., pumps, boilers, elevation).
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Q25.Laboratory faucets with hose connections must be protected by:
A.A standard check valveB.A vacuum breakerC.A trap primerD.An expansion tankB. A vacuum breakerExplanation: Hose connections always present a backsiphonage risk and require vacuum breaker protection.
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Q26.Double Check Valve Assemblies (DCVA) consist of:
A.Two independently acting check valvesB.Two check valves and a relief portC.One check valve and one air inletD.Two gate valves onlyA. Two independently acting check valvesExplanation: DCVAs have two redundant check valves. Unlike RPZs, they do NOT have a relief zone that opens to atmosphere.
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Q27.Which backflow preventer must be removed or protected during freezing conditions if installed outdoors?
A.PVBB.RPZC.DCVAD.All of the aboveD. All of the aboveExplanation: All backflow devices holding water can freeze and crack. They must be protected (heated enclosure) or removed/drained.
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Q28.A 'Break Tank' is used to:
A.Store hot waterB.Create an air gap separation between the potable supply and a booster pumpC.Catch leaksD.Break down sewageB. Create an air gap separation between the potable supply and a booster pumpExplanation: A break tank is a non-pressurized tank with an air gap on the inlet, used to supply pumps without risking backflow to the mains.
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Q29.The critical level of a vacuum breaker on a urinal flushometer must be installed at least ___ inches above the spill line of the bowl.
A.4B.6C.12D.18B. 6Explanation: IPC 608.13.6 requires a minimum of 6 inches for AVBs/vacuum breakers on flushometers.
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Q30.Deck-mounted bath/shower faucets with a hand-held spray must have:
A.A check valve in the hoseB.An integral vacuum breaker or ASSE 1014 protectionC.No protectionD.A filterB. An integral vacuum breaker or ASSE 1014 protectionExplanation: Handheld sprays can fall into the tub water (submerged inlet), creating a backsiphonage hazard. They require vacuum breaker protection.
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