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Journeyman Plumber practice questions

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Question 1Plumbing Code and Regulations

What is the minimum water seal depth required for a plumbing trap?

  1. 2 inches Correct answer.
  2. 1 inch
  3. 6 inches
  4. 4 inches

Explanation

A plumbing trap must maintain a water seal of at least 2 inches and no more than 4 inches. The minimum prevents sewer gas passage, while the maximum prevents excessive seal that could be difficult to maintain.

Question 2Plumbing Code and Regulations

What is the minimum slope for a 3-inch horizontal drainage pipe?

  1. 1/16 inch per foot
  2. 1/2 inch per foot
  3. 1/4 inch per foot
  4. 1/8 inch per foot Correct answer.

Explanation

Horizontal drainage pipe 3 inches and larger may be installed at a minimum slope of 1/8 inch per foot, which is about 1 percent. Smaller pipe, such as 2-inch and below, generally requires 1/4 inch per foot.

Question 3Plumbing Code and Regulations

What is the minimum air gap for a water-supply outlet discharging into a fixture?

  1. 1 inch or twice the diameter of the effective opening, whichever is greater Correct answer.
  2. 2 inches
  3. 1/2 inch
  4. 6 inches

Explanation

An air gap must provide at least 1 inch or twice the diameter of the effective opening, whichever is greater, measured above the flood level rim. This physical separation protects the potable water supply from contamination.

Question 4Plumbing Code and Regulations

Which backflow prevention assembly protects against both backsiphonage and backpressure by maintaining a pressure differential?

  1. Atmospheric vacuum breaker
  2. Air gap
  3. Double check valve assembly
  4. Reduced pressure principle assembly Correct answer.

Explanation

A reduced pressure principle assembly uses two check valves and a differential relief valve that opens when pressure reverses. It protects against both backsiphonage and backpressure.

Question 5Plumbing Code and Regulations

How must a temperature and pressure relief valve discharge pipe terminate?

  1. Not more than 6 inches above the floor or receptor Correct answer.
  2. Directly connected to the drainage system
  3. With a threaded cap on the end
  4. Reduced to a smaller diameter at the outlet

Explanation

The discharge pipe from a temperature and pressure relief valve must terminate not more than 6 inches above the floor or a receptor. It must not be directly connected to drainage, threaded, or reduced in size.

Question 6Plumbing Code and Regulations

Under lead-free plumbing requirements, what is the maximum weighted average lead content of wetted surfaces?

  1. 0.5 percent
  2. 0.25 percent Correct answer.
  3. 2 percent
  4. 0.2 percent

Explanation

Lead-free plumbing materials are defined as having not more than 0.25 percent weighted average lead content on wetted surfaces. This limit applies to pipes, fittings, and fixtures used for potable water.

Question 7Plumbing Code and Regulations

How far must a vent pipe extend above a flat roof?

  1. 6 inches Correct answer.
  2. 12 inches
  3. 4 inches
  4. 2 inches

Explanation

A vent terminal must extend at least 6 inches above the roof surface. If the roof is used for purposes other than weather protection, the vent must extend at least 7 feet above the roof.

Question 8Plumbing Code and Regulations

Which material is prohibited for potable water piping in new plumbing installations?

  1. PEX
  2. CPVC
  3. Copper
  4. Lead Correct answer.

Explanation

Lead pipe is prohibited for potable water piping because of its health hazards. Approved materials must be lead-free and listed for potable water use.

Question 9Plumbing Code and Regulations

In plumbing code, what is the building drain?

  1. The vertical main vent extending through the roof
  2. The piping that collects storm water from the roof
  3. The lowest piping that receives soil, waste, and other drainage inside the building and conveys it to the building sewer Correct answer.
  4. The pipe that carries water from the water main to the building

Explanation

The building drain is the lowest piping of the drainage system inside the building. It receives soil, waste, and other drainage and ends at the building sewer.

Question 10Plumbing Code and Regulations

What is the minimum size of a vent pipe for a fixture drain with a 2-inch trap?

  1. 1-1/2 inches
  2. 1 inch
  3. 2 inches
  4. 1-1/4 inches Correct answer.

Explanation

A vent must be at least one-half the diameter of the drain it serves and not less than 1-1/4 inches. Half of a 2-inch drain is 1 inch, so the 1-1/4-inch minimum governs.

Question 11Plumbing Code and Regulations

What is the maximum horizontal support spacing for 1-inch copper tubing?

  1. 10 feet
  2. 6 feet Correct answer.
  3. 4 feet
  4. 5 feet

Explanation

Copper tubing up to 1 inch in diameter must be supported at intervals not exceeding 6 feet. Larger tubing may be permitted longer spacing depending on the code table.

Question 12Plumbing Code and Regulations

A pressure-reducing valve is generally required when the static water pressure exceeds what value?

  1. 50 psi
  2. 80 psi Correct answer.
  3. 75 psi
  4. 60 psi

Explanation

Where static water pressure exceeds 80 psi, a pressure-reducing valve is required. A closed system with a pressure-reducing valve also needs thermal expansion control.

Question 13Plumbing Code and Regulations

What is the minimum nominal diameter of a building sewer?

  1. 3 inches Correct answer.
  2. 2 inches
  3. 2-1/2 inches
  4. 4 inches

Explanation

A building sewer must be at least 3 inches in nominal diameter. Larger sizes may be required by the drainage load or local conditions.

Question 14Plumbing Code and Regulations

What is the minimum clearance from the centerline of a water closet to a side wall?

  1. 15 inches Correct answer.
  2. 12 inches
  3. 18 inches
  4. 24 inches

Explanation

A water closet must be installed with at least 15 inches of clearance from its centerline to a side wall. This provides usable space and access for the occupant.

Question 15Plumbing Code and Regulations

What is the minimum clear width of a water closet compartment?

  1. 24 inches
  2. 28 inches
  3. 36 inches
  4. 30 inches Correct answer.

Explanation

A water closet compartment must be at least 30 inches in clear width. The compartment depth and door arrangement are also regulated.

Question 16Plumbing Code and Regulations

Where is a cleanout required on a vertical drainage stack?

  1. At each floor level where fixtures connect
  2. At the base of the stack above the building drain Correct answer.
  3. At the top of the stack above the roof
  4. At the midpoint of the vertical stack

Explanation

A cleanout is required at the base of a vertical drainage stack where it connects to the building drain. Additional cleanouts may be required on long horizontal runs.

Question 17Plumbing Code and Regulations

What is the maximum developed length of a 1-1/2-inch trap arm from the trap weir to the vent?

  1. 8 feet
  2. 3 feet 6 inches
  3. 5 feet
  4. 6 feet Correct answer.

Explanation

The trap arm length is limited to prevent self-siphonage of the trap. For a 1-1/2-inch trap arm, the maximum developed length is 6 feet.

Question 18Plumbing Code and Regulations

A fixture drain is installed below the flood level rim of the nearest upstream manhole. What device is required?

  1. Air admittance valve
  2. Pressure-reducing valve
  3. Backwater valve Correct answer.
  4. Vacuum breaker

Explanation

A backwater valve is required where a fixture drain is below the flood level rim of the nearest upstream manhole. It prevents sewage from backing up into the building.

Question 19Plumbing Code and Regulations

Where must the temperature and pressure relief valve be located on a storage water heater?

  1. Within the top 6 inches of the tank Correct answer.
  2. On the cold water inlet pipe
  3. At the bottom drain valve
  4. On the discharge pipe 12 inches from the tank

Explanation

The temperature and pressure relief valve must be located within the top 6 inches of the storage tank. This is where the hottest water collects and where overheating is detected.

Question 20Plumbing Code and Regulations

A drainage system is tested with water. What is the minimum head required at the highest point?

  1. 5 feet
  2. 10 feet Correct answer.
  3. 15 feet
  4. 20 feet

Explanation

A water test of the drainage system requires a minimum head of 10 feet at the highest point of the system. The test is typically held for at least 15 minutes.

Question 21Plumbing Code and Regulations

Where is a sump pump allowed to discharge?

  1. Into a septic tank
  2. Into the sanitary sewer
  3. Into the building drain through a trap
  4. To the storm drainage system or exterior grade Correct answer.

Explanation

Sump pumps handle groundwater or stormwater and must discharge to an approved storm drainage system or exterior grade. Discharging into the sanitary sewer can overload the system.

Question 22Plumbing Code and Regulations

A grease interceptor is required for which type of establishment?

  1. A dental office
  2. A car wash
  3. A coin laundry
  4. A commercial food service establishment Correct answer.

Explanation

Commercial food service establishments produce grease-laden waste and require a grease interceptor. The interceptor keeps fats, oils, and grease out of the drainage system.

Question 23Plumbing Code and Regulations

A closed water supply system with a backflow preventer or pressure-reducing valve requires what additional device to control thermal expansion?

  1. Air admittance valve
  2. Vacuum relief valve
  3. Expansion tank Correct answer.
  4. Check valve

Explanation

A closed system prevents expanded water from backing into the main, so an expansion tank is required to absorb thermal expansion. Without it, pressure can rise and damage the system.

Question 24Plumbing Code and Regulations

What is the maximum height of a lavatory rim in an accessible bathroom?

  1. 36 inches
  2. 31 inches
  3. 29 inches
  4. 34 inches Correct answer.

Explanation

An accessible lavatory rim must be no higher than 34 inches above the finished floor. Knee and toe clearance are also required beneath the fixture.

Question 25Plumbing Code and Regulations

When must a plumbing permit be obtained?

  1. Only for commercial work
  2. Before work begins Correct answer.
  3. After rough-in inspection
  4. When the building is sold

Explanation

A plumbing permit must be obtained before work begins, except for minor repairs specifically exempted by code. Required inspections are then made at specified stages of construction.

Question 26Plumbing Code and Regulations

What is the minimum depth of water seal required for a plumbing trap?

  1. 2 inches Correct answer.
  2. 3 inches
  3. 4 inches
  4. 6 inches

Explanation

A trap must hold a water seal of not less than 2 inches and not more than 4 inches, measured between the trap weir and the top of the trap dip. The 2-inch minimum keeps sewer gas from passing through ordinary pressure fluctuations.

Question 27Plumbing Code and Regulations

What is the minimum slope permitted for a 4-inch horizontal drainage pipe?

  1. 1/2 inch per foot
  2. 1/8 inch per foot Correct answer.
  3. 1/4 inch per foot
  4. 1/16 inch per foot

Explanation

Drainage pipe slope is set by pipe size: 2-1/2 inches and smaller require 1/4 inch per foot, 3-inch through 6-inch pipe requires 1/8 inch per foot, and 8-inch and larger requires 1/16 inch per foot. A 4-inch pipe therefore needs at least 1/8 inch per foot.

Question 28Plumbing Code and Regulations

How far must a plumbing vent terminal be kept from a door, window, or gravity air inlet of a building?

  1. 5 feet
  2. 20 feet
  3. 3 feet
  4. 10 feet Correct answer.

Explanation

Vent terminals must be located at least 10 feet from any door, window, or gravity air inlet into a building so that the vent discharge does not re-enter occupied space. Terminals must also meet the required height above the roof surface.

Question 29Plumbing Code and Regulations

A fixture outlet has an effective opening of 1 inch. What is the minimum air gap required to protect the potable water supply?

  1. 2 inches Correct answer.
  2. 3 inches
  3. 1-1/2 inches
  4. 1 inch

Explanation

An air gap must be at least twice the diameter of the effective opening of the outlet and never less than 1 inch. For a 1-inch effective opening, twice the opening equals 2 inches, so that becomes the controlling minimum.

Question 30Plumbing Code and Regulations

A kitchen sink is set in a counter island with no wall or partition within the required venting distance. Which venting arrangement does the code permit for the sink?

  1. A bypass vent taken off the stack above the highest branch
  2. A relief vent one pipe size larger than the drain
  3. An island fixture vent (loop vent) Correct answer.
  4. A continuous waste and vent shared with an adjacent sink

Explanation

Island fixture venting uses a loop taken off the drain below the trap and returned to the drain or stack, giving the fixture a vent path without a wall to run a conventional vent up through. The loop must be installed with its own cleanout and arranged so the drain below the fixtures acts as the vent.

Question 31Drainage, Waste, and Vent Systems

What is the minimum water seal depth required for a plumbing fixture trap?

  1. 2 inches Correct answer.
  2. 4 inches
  3. 3 inches
  4. 1 inch

Explanation

A fixture trap must hold a liquid seal of at least 2 inches and no more than 4 inches, which resists sewer gas while keeping the trap from holding an excessive weight of water.

Question 32Drainage, Waste, and Vent Systems

Why is an S-trap prohibited in a drainage system?

  1. It siphons its own seal as waste discharges Correct answer.
  2. It is difficult to clean
  3. It is larger than a P-trap
  4. It requires an extra vent

Explanation

An S-trap discharges into an immediate downward drop after the trap, so the slug of waste water starts a siphon that pulls the seal out of the trap and allows sewer gas into the building.

Question 33Drainage, Waste, and Vent Systems

The trap arm is the portion of a fixture drain that runs from the trap weir to what point?

  1. The building drain
  2. The vent connection Correct answer.
  3. The fixture outlet
  4. The stack fitting

Explanation

The trap arm is the section of fixture drain between the trap weir and the point where that drain is vented. Its length is limited so the trap cannot self-siphon.

Question 34Drainage, Waste, and Vent Systems

Where a roof is not used for purposes other than weather protection, a vent stack must terminate at least how far above the roof surface?

  1. 18 inches
  2. 12 inches
  3. 2 inches
  4. 6 inches Correct answer.

Explanation

Vent terminals must extend at least 6 inches above the roof line. Where the roof is used for other purposes, the required height increases to 12 inches.

Question 35Drainage, Waste, and Vent Systems

Horizontal drainage piping that is 2-1/2 inches in diameter and smaller must be installed at what minimum slope?

  1. 1/2 inch per foot
  2. 1/4 inch per foot Correct answer.
  3. 1/16 inch per foot
  4. 1/8 inch per foot

Explanation

Small-diameter drain pipe needs at least 1/4 inch per foot of fall, roughly two percent, to keep solids moving. Flatter slopes are permitted only for larger pipe sizes.

Question 36Drainage, Waste, and Vent Systems

What is the smallest diameter permitted for an individual fixture vent?

  1. 1 inch
  2. 1-1/4 inch Correct answer.
  3. 3/4 inch
  4. 2 inch

Explanation

An individual fixture vent may not be smaller than 1-1/4 inches, and it must also be sized from the fixture-unit table so it is never smaller than the drain it serves.

Question 37Drainage, Waste, and Vent Systems

How many fixtures may discharge through a single trap?

  1. Three, if a common vent is installed
  2. One Correct answer.
  3. Two, if they are on the same floor
  4. Any number, if the trap is oversized

Explanation

Each fixture must be trapped separately, except for fixtures that are listed and installed as a single unit. A shared trap cannot be vented properly and will siphon.

Question 38Drainage, Waste, and Vent Systems

A floor drain in an unused warehouse loses its trap seal after several months. Which is the most likely cause?

  1. Capillary action in the drain pipe
  2. Back pressure from the sewer
  3. Momentum from a slug of waste
  4. Evaporation of the seal water Correct answer.

Explanation

A trap that receives no water for a long period dries out as the seal evaporates. Trap primers are installed to keep such seals full.

Question 39Drainage, Waste, and Vent Systems

What is the minimum size of the fixture drain serving a water closet?

  1. 2 inches
  2. 3 inches Correct answer.
  3. 2-1/2 inches
  4. 4 inches

Explanation

A water closet requires a drain and trap of at least 3 inches so the flush volume and solid waste can pass without clogging.

Question 40Drainage, Waste, and Vent Systems

What is the minimum trap size for a kitchen sink?

  1. 2 inch
  2. 3 inch
  3. 1-1/2 inch Correct answer.
  4. 1-1/4 inch

Explanation

A kitchen sink needs a trap of at least 1-1/2 inches because of the grease and food solids it carries. A lavatory, by comparison, may use a 1-1/4 inch trap.

Question 41Drainage, Waste, and Vent Systems

How must a domestic dishwasher drain be connected to the plumbing system?

  1. Directly to the trap arm, downstream of the trap
  2. To the sink tailpiece, upstream of the trap Correct answer.
  3. To the soil stack above the highest fixture served
  4. To the floor drain through a backwater valve

Explanation

The dishwasher must discharge on the fixture side of the trap and be protected by an air gap or a high loop, so waste water cannot back up into the appliance and sewer gas cannot reach it.

Question 42Drainage, Waste, and Vent Systems

Why is a trap primer installed at a floor drain?

  1. To add water to the trap to replace evaporation Correct answer.
  2. To prevent reverse flow during a sewer backup
  3. To admit air when the drain is used
  4. To strain solids before they enter the trap

Explanation

A trap primer delivers a small amount of water to the trap on a regular basis, keeping the seal intact where the fixture receives little or no normal flow.

Question 43Drainage, Waste, and Vent Systems

How does an air admittance valve function?

  1. It opens to admit air when the drain is under negative pressure and closes under positive pressure Correct answer.
  2. It terminates the vent stack above the roof
  3. It serves as both a vent and a wet vent for two fixtures
  4. It relieves positive pressure in the building drain by venting to the outdoors

Explanation

An air admittance valve is a one-way device that opens on negative pressure to protect the trap seal and closes when pressure in the system is positive, keeping sewer gas inside the piping.

Question 44Drainage, Waste, and Vent Systems

A fixture is installed so that its flood level rim is below the level of the next upstream manhole cover. What must be provided?

  1. A backwater valve on the fixture drain Correct answer.
  2. A cleanout at the fixture
  3. A relief vent at the fixture
  4. A trap primer at the fixture

Explanation

Fixtures set below the upstream manhole elevation can be flooded by sewage backing up out of the public sewer, so a backwater valve must protect the drain serving them.

Question 45Drainage, Waste, and Vent Systems

Which fitting is used where a horizontal drain changes direction 90 degrees?

  1. A vent tee
  2. A double sanitary tee
  3. A combination wye with an eighth bend Correct answer.
  4. A sanitary tee

Explanation

A horizontal-to-horizontal change of direction needs a fitting that gives a smooth sweep, typically a wye with an eighth bend or a pair of 45-degree bends.

Question 46Drainage, Waste, and Vent Systems

Which fitting is appropriate where a horizontal fixture drain connects into a vertical soil stack?

  1. A sanitary tee Correct answer.
  2. A double sanitary tee
  3. A wye
  4. A combination wye with an eighth bend

Explanation

A sanitary tee has a curved branch that turns the flow downward in the direction of stack flow, making it the standard fitting for a horizontal branch entering a vertical stack.

Question 47Drainage, Waste, and Vent Systems

Where a soil or waste stack connects to a horizontal building drain, what must be provided?

  1. A backwater valve
  2. A trap primer
  3. A vent at the base
  4. A cleanout at the base of the stack Correct answer.

Explanation

A cleanout is required at the base of each stack so the stack bottom and the horizontal drain can be rodded without removing fixtures or breaking piping.

Question 48Drainage, Waste, and Vent Systems

A vent terminal on a roof must be at least how far horizontally from an openable window, door, or outdoor air intake?

  1. 20 feet
  2. 3 feet
  3. 10 feet Correct answer.
  4. 5 feet

Explanation

Vent terminals must be kept at least 10 feet horizontally from windows, doors, and air intakes so sewer gas cannot re-enter the building, unless the terminal is raised at least 3 feet above the opening.

Question 49Drainage, Waste, and Vent Systems

A vent is connected to a fixture drain within 2 pipe diameters of the trap weir. Why is this prohibited?

  1. It makes the trap too deep
  2. It prevents the vent from being rodded
  3. It forms a crown vent that can siphon the seal Correct answer.
  4. It reduces the drain size below the trap size

Explanation

The vent must be far enough downstream that water in the trap cannot bridge to the vent opening and start a siphon. A connection made too close to the weir is a crown vent.

Question 50Drainage, Waste, and Vent Systems

Horizontal PVC DWV pipe must be supported at intervals not exceeding what distance?

  1. 2 feet
  2. 10 feet
  3. 4 feet Correct answer.
  4. 8 feet

Explanation

Plastic DWV pipe is supported at intervals of no more than 4 feet, and also at each joint or fitting, so the pipe does not sag and hold water.