Master / Journeyman Plumber Exam
Gas Piping Practice Questions
25 practice questions with detailed explanations — aligned to the Master / Journeyman Plumber Exam.
Q1.According to the IFGC, what is the minimum test pressure required for a gas piping system withstand test?
A.1.5 times the working pressure, but not less than 3 psigB.10 psigC.20 psigD.1.5 times the working pressure, but not less than 5 psigA. 1.5 times the working pressure, but not less than 3 psigExplanation: IFGC 406.4.1 requires the test pressure to be 1.5 times the proposed maximum working pressure, but generally not less than 3 psig.
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Q2.The test duration for a gas piping system with a test pressure of less than 10 psig shall be not less than:
A.10 minutesB.15 minutesC.30 minutesD.1 hourA. 10 minutesExplanation: IFGC 406.4.2 states the test duration shall be not less than 10 minutes.
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Q3.Gas shutoff valves shall be located within ___ feet of the appliance they serve.
A.3B.4C.5D.6D. 6Explanation: IFGC 409.5.1 requires the shutoff valve to be located in the same room as the appliance and within 6 feet of the appliance.
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Q4.Plastic pipe (PE, PVC) used for gas piping shall be installed:
A.Indoors onlyB.Outdoors underground onlyC.In atticsD.AnywhereB. Outdoors underground onlyExplanation: IFGC 403.6 prohibits plastic pipe for use within buildings. It is allowed outdoors underground only.
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Q5.What is the minimum burial depth for underground gas piping?
A.6 inchesB.12 inchesC.18 inchesD.24 inchesB. 12 inchesExplanation: IFGC 404.12 requires gas piping underground to be installed not less than 12 inches below grade (except for individual lines to outdoor lights/grills which can be 8 inches if protected).
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Q6.A sediment trap (drip leg) is required:
A.At the utility meter onlyB.Downstream of the appliance shutoff valve as close to the inlet of the equipment as practicalC.On all gas lines exceeding 20 feetD.Upstream of the shutoff valveB. Downstream of the appliance shutoff valve as close to the inlet of the equipment as practicalExplanation: IFGC 408.4 requires sediment traps (often called dirt legs) to be installed downstream of the appliance shutoff valve to catch debris before it enters the gas valve.
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Q7.The unthreaded portion of gas piping outlets shall extend not less than ___ inches through finished ceilings or walls.
A.1B.1-1/2C.2D.2-1/2A. 1Explanation: IFGC 404.16 requires the unthreaded portion of piping outlets to extend at least 1 inch beyond finished ceilings or walls.
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Q8.Standard Method: The minimum required volume of indoor combustion air is ___ cubic feet per 1,000 BTU/h of the appliance input rating.
A.25B.50C.100D.200B. 50Explanation: IFGC 304.5.1 states the minimum volume shall be 50 cubic feet per 1,000 BTU/h.
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Q9.Unvented room heaters shall not be installed in:
A.Living roomsB.KitchensC.Sleeping rooms or bathrooms (with limited exceptions)D.GaragesC. Sleeping rooms or bathrooms (with limited exceptions)Explanation: IFGC 303.3 prohibits unvented fuel-burning heaters in bedrooms or bathrooms (unless it's a specific wall-mounted heater equipped with an oxygen depletion sensor and meets BTU limits).
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Q10.Gas piping installed in a concealed location shall not contain:
A.Threaded elbowsB.Unions, tubing fittings, or running threadsC.Welded jointsD.CouplingsB. Unions, tubing fittings, or running threadsExplanation: IFGC 404.5 prohibits unions, tubing fittings, right/left couplings, bushings, compression couplings, and running threads in concealed locations (walls/floors) to prevent leaks.
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Q11.Appliance fuel connectors shall have a maximum overall length of:
A.3 feetB.4 feetC.6 feetD.10 feetC. 6 feetExplanation: IFGC 411.1.3.1 limits the length of flexible appliance connectors to 6 feet.
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Q12.CSST (Corrugated Stainless Steel Tubing) gas piping systems must be:
A.Painted yellowB.Electrically bonded (grounded)C.Buried at least 24 inchesD.Used for vents onlyB. Electrically bonded (grounded)Explanation: IFGC 310.1.1 requires CSST to be bonded to the electrical service grounding electrode system to prevent arc damage from lightning strikes.
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Q13.Underground gas piping carrying Propane (LPG) allows:
A.Use of standard Schedule 40 PVCB.Use of PE pipe (Yellow)C.Use of Type M copperD.Use of cast ironB. Use of PE pipe (Yellow)Explanation: Polyethylene (PE) is the standard plastic allowed for underground gas (Natural or LP). Schedule 40 PVC is generally prohibited for gas due to brittleness.
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Q14.Supports for 3/4-inch rigid steel gas pipe shall be spaced not more than ___ feet apart.
A.6B.8C.10D.12B. 8Explanation: IFGC Table 415.1 requires 3/4-inch or 1-inch steel pipe to be supported every 8 feet. (1/2-inch is 6 feet).
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Q15.A gas vent connector shall slope upward toward the vent or chimney at least:
A.1/8 inch per footB.1/4 inch per footC.1/2 inch per footD.1 inch per footB. 1/4 inch per footExplanation: IFGC 503.10.7 requires a minimum upward slope of 1/4 inch per foot to ensure draft.
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Q16.Where gas piping penetrates a foundation wall underground, it must be:
A.Encased in a protective sleeveB.PaintedC.GluedD.Made of copperA. Encased in a protective sleeveExplanation: IFGC 404.6 requires piping passing through a foundation wall to be encased in a protective sleeve and sealed to prevent gas entry into the building.
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Q17.Liquefied Petroleum Gas (LPG) is heavier than air. Natural Gas is:
A.Heavier than airB.Lighter than airC.The same density as airD.A liquidB. Lighter than airExplanation: Natural gas (Methane) is lighter than air (Specific Gravity ~0.60), causing it to rise and dissipate. Propane is heavier (SG ~1.50) and pools in low spots.
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Q18.Thread joint compounds (pipe dope) used on gas piping must be:
A.Water solubleB.Resistant to the action of Liquefied Petroleum (LP) gasC.ClearD.Applied to female threads onlyB. Resistant to the action of Liquefied Petroleum (LP) gasExplanation: IFGC 403.9.3 requires pipe joint compound to be resistant to the chemical action of LP gas.
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Q19.When using the 'Longest Length Method' to size gas piping, you measure from the point of delivery (meter) to:
A.The first applianceB.The water heaterC.The most remote outletD.The middle of the systemC. The most remote outletExplanation: The Longest Length Method requires measuring from the delivery point to the most remote outlet, then using that single length to size the entire system.
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Q20.Underground gas piping marked with a yellow tracer wire is likely:
A.Steel pipeB.Polyethylene (PE) plastic pipeC.Copper pipeD.Aluminum pipeB. Polyethylene (PE) plastic pipeExplanation: Plastic pipe is non-conductive, so IFGC 404.17.3 requires an electrically continuous yellow tracer wire (minimum AWG 18) to be installed with it for locating purposes.
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Q21.Category I gas appliances rely on:
A.Natural draft (non-positive vent pressure)B.Forced draftC.Positive vent pressureD.Condensing technologyA. Natural draft (non-positive vent pressure)Explanation: Category I appliances operate with a non-positive vent static pressure and a vent gas temperature that avoids excessive condensation (standard atmospheric draft).
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Q22.Which valve is prohibited for use as a gas shutoff valve?
A.Ball valveB.Lubricated plug cockC.Water valve (Gate valve)D.Gas cockC. Water valve (Gate valve)Explanation: Gas valves must be approved for gas service (often marked WOG or Gas). Standard water gate valves are not approved for gas isolation.
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Q23.Gas piping shall not be used as a:
A.Fuel lineB.Grounding electrodeC.Support for other pipingD.Conduit for wiresB. Grounding electrodeExplanation: IFGC 310.1 prohibits using gas piping as a grounding electrode (ground rod). It must be bonded *to* the ground, but not used *as* the ground path for the electrical system.
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Q24.The approximate BTU content of 1 cubic foot of Natural Gas is:
A.500 BTUB.1,000 BTUC.2,500 BTUD.10,000 BTUB. 1,000 BTUExplanation: Standard natural gas contains approximately 1,000 to 1,050 BTUs per cubic foot. (Propane is ~2,500).
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Q25.When purging a gas line of air, if the piping is larger than ___ inches, the purge gas must be discharged outdoors.
A.2B.2-1/2C.3D.4A. 2Explanation: Wait, let's verify. IFGC 406.7.2. Piping systems where the tubing size is up to 2 inches can be purged indoors (with precautions). Larger or longer runs typically require outdoor discharge to prevent dangerous gas accumulation. Specifically, IFGC 406.7.1 allows indoor discharge for specific volumes. However, 406.7.2 mandates outdoor discharge for piping >2 inches nominal size (depending on length/pressure). Let's use the 2021 specific text: '...shall be discharged to the outdoors... where the piping design pressure exceeds 2 psig... or the piping is greater than 2 inches'.
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