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NH Journeyman Plumber practice questions

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Question 1General Plumbing Knowledge

According to the New Hampshire plumbing code, what is the minimum size of a building sewer serving a single-family dwelling?

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

Explanation

The building sewer for a single-family dwelling must be at least 3 inches in diameter under the adopted plumbing code. A 4-inch sewer is common but is not the required minimum for a single dwelling.

Question 2General Plumbing Knowledge

What is the standard vertical distance a water closet drain must drop to the building drain for gravity flow, expressed as the required slope for a 3-inch horizontal drain?

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

Explanation

A 3-inch horizontal drainage pipe must be installed at a slope of not less than 1/4 inch per foot. This slope provides adequate scouring velocity while maintaining proper venting.

Question 3General Plumbing Knowledge

A fixture trap seal must be maintained to prevent sewer gas from entering a building. What is the minimum trap seal depth required by code?

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

Explanation

The code requires a liquid trap seal of not less than 2 inches and not more than 4 inches in depth. This range prevents sewer gas passage while avoiding excessive seal depth that could hold debris.

Question 4General Plumbing Knowledge

What is the purpose of a vent stack in a plumbing drainage system?

  1. To collect and remove storm water from the roof
  2. To provide additional drainage capacity during peak flow
  3. To admit air into the system to protect trap seals Correct answer.
  4. To serve as a cleanout access point for the building drain

Explanation

A vent stack admits air into the drainage system so that pressure differentials do not siphon or blow out trap seals. It equalizes pressure and allows proper gravity flow of waste.

Question 5General Plumbing Knowledge

What minimum air gap is required between a fixture outlet and the flood-level rim of a receptacle for an air gap to be considered acceptable?

  1. Three inches fixed regardless of pipe size
  2. Two times the outlet diameter only
  3. One-half the diameter of the outlet
  4. One inch or twice the outlet diameter, whichever is greater Correct answer.

Explanation

An acceptable air gap is at least twice the effective opening of the outlet, with a minimum of 1 inch. This prevents backflow by maintaining a physical separation between the potable supply and any contamination.

Question 6General Plumbing Knowledge

A horizontal branch serving a water closet must connect to a vertical stack. What fitting type is required where the branch changes direction from horizontal to vertical?

  1. Wye branch with 45-degree bend Correct answer.
  2. Double sanitary tee
  3. Long-turn 90-degree elbow
  4. Sanitary tee

Explanation

Where a horizontal drain turns to vertical, a wye fitting combined with a 45-degree bend is required to provide a smooth sweeping flow. Sanitary tees are prohibited in this orientation because they cause turbulence and clogging.

Question 7General Plumbing Knowledge

What is the required minimum diameter of a soil stack serving a water closet in a residential building?

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

Explanation

A soil stack receiving a water closet discharge must be at least 3 inches in diameter. The 3-inch minimum accommodates the solid waste and volume from a water closet.

Question 8General Plumbing Knowledge

A plumbing system uses a 4-inch building drain with a slope of 1/8 inch per foot. Which condition must be satisfied for this slope to be permitted?

  1. The drain must be installed below a concrete slab
  2. The drain must carry only clear water waste
  3. The drain must be a 4-inch or larger pipe with adequate velocity Correct answer.
  4. The drain must be connected to a sump pump

Explanation

A slope of 1/8 inch per foot is permitted only for pipes 4 inches and larger, and the design must ensure adequate scouring velocity. Smaller drains cannot use this reduced slope.

Question 9General Plumbing Knowledge

What is the maximum developed length permitted for a fixture trap arm before a vent must be provided?

  1. There is no limit as long as the trap is vented at the stack
  2. The trap arm may not exceed twice its diameter in feet
  3. The trap arm may not exceed the distance from the trap weir to the vent fitting as limited by code table Correct answer.
  4. The trap arm may not exceed the distance equal to its diameter in feet

Explanation

The trap arm length is limited by code tables based on pipe diameter to prevent self-siphoning of the trap seal. The distance is measured from the trap weir to the vent connection.

Question 10General Plumbing Knowledge

A water heater is installed in a dwelling. What is the required maximum temperature setting for the relief valve on a residential water heater?

  1. 120 degrees Fahrenheit
  2. 210 degrees Fahrenheit Correct answer.
  3. 150 degrees Fahrenheit
  4. 180 degrees Fahrenheit

Explanation

A temperature relief valve on a residential water heater is typically set to open at a maximum of 210 degrees Fahrenheit. This protects against excessive temperature and pressure in the tank.

Question 11General Plumbing Knowledge

What is the minimum required size of a water service pipe for a single-family dwelling based on the standard sizing method?

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

Explanation

The minimum water service pipe size for a single-family dwelling is 3/4 inch under the standard sizing tables. Smaller sizes cannot deliver adequate flow for typical residential demand.

Question 12General Plumbing Knowledge

A backflow preventer is installed on a lawn irrigation system connected to the potable water supply. Which device provides the appropriate protection for this application?

  1. Air gap fitting
  2. Pressure vacuum breaker assembly Correct answer.
  3. Double check valve assembly
  4. Atmospheric vacuum breaker

Explanation

A pressure vacuum breaker assembly is approved for irrigation systems because it protects against both backsiphonage and backpressure. It must be installed above the highest downstream outlet.

Question 13General Plumbing Knowledge

What is the required clearance between a water heater and combustible material when no listed clearance is provided by the manufacturer?

  1. 18 inches
  2. 6 inches
  3. 12 inches Correct answer.
  4. 24 inches

Explanation

Where the manufacturer does not specify a clearance, the code requires at least 12 inches between a water heater and combustible material. Listed clearances on the appliance take precedence when provided.

Question 14General Plumbing Knowledge

A lavatory drain is installed with a 1-1/4 inch trap arm. What is the maximum length of the trap arm permitted before venting is required?

  1. 42 inches
  2. 30 inches Correct answer.
  3. 12 inches
  4. 24 inches

Explanation

For a 1-1/4 inch trap arm, the code table limits the developed length to 30 inches from the trap weir to the vent. This prevents self-siphoning of the trap seal.

Question 15General Plumbing Knowledge

What is the purpose of a cleanout in a drainage system?

  1. To provide access for clearing blockages in the drain Correct answer.
  2. To measure flow in the building drain
  3. To prevent backflow into the potable water supply
  4. To vent the drainage system to the outdoors

Explanation

A cleanout provides an accessible opening for removing blockages from drainage piping. It must be installed at specified locations such as the base of stacks and ends of horizontal runs.

Question 16General Plumbing Knowledge

A horizontal wet vent is used to vent a bathroom group. Which condition must be met for a horizontal wet vent to be permitted?

  1. The wet vent must be constructed of cast iron only
  2. The wet vent must be installed below the fixture it serves
  3. The wet vent must be at least 1-1/2 inches in diameter and slope at 1/8 inch per foot
  4. The wet vent must be at least 2 inches in diameter and connect to a vertical stack Correct answer.

Explanation

A horizontal wet vent must be sized at least 2 inches and connect to a vertical stack to function properly. It carries waste from one fixture while venting another in the same bathroom group.

Question 17General Plumbing Knowledge

A building has a 4-inch building drain and a 4-inch building sewer. What is the minimum slope for the building sewer when the pipe is 4 inches in diameter?

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

Explanation

A 4-inch building sewer may be installed at a minimum slope of 1/8 inch per foot because the larger diameter provides adequate velocity. Smaller drains require a steeper slope.

Question 18General Plumbing Knowledge

What is the minimum size of a vent pipe serving a water closet?

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

Explanation

The vent for a water closet must be at least 1-1/2 inches in diameter. This size ensures adequate air flow to protect the trap seal during flushing.

Question 19General Plumbing Knowledge

A water distribution system uses a pressure-reducing valve because the street pressure is 120 psi. What is the typical maximum pressure that a PRV should deliver to the building?

  1. 80 psi Correct answer.
  2. 120 psi
  3. 100 psi
  4. 50 psi

Explanation

A pressure-reducing valve is typically set to deliver no more than 80 psi to the building distribution system. Pressures above this can damage fixtures and appliances.

Question 20General Plumbing Knowledge

What is the required minimum size for a floor drain trap arm serving a floor drain in a commercial kitchen?

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

Explanation

Floor drains in commercial kitchens typically require a 2-inch trap arm to handle the waste flow and maintain the trap seal. The size is set by the fixture drain requirements in the code.

Question 21General Plumbing Knowledge

What is the minimum required size of a vent terminal above the roof for a 3-inch vent stack?

  1. The vent must extend at least 12 inches above the roof
  2. The vent must extend at least 18 inches above the roof
  3. The vent must extend at least 24 inches above the roof
  4. The vent must extend at least 6 inches above the roof Correct answer.

Explanation

A vent terminal must extend at least 6 inches above the roof surface to prevent blockage by snow and debris. Larger clearances may be required near windows or in high-snow areas.

Question 22General Plumbing Knowledge

A plumbing fixture is installed in a public restroom. What is the required maximum water temperature delivered to a public lavatory to prevent scalding?

  1. 140 degrees Fahrenheit
  2. 120 degrees Fahrenheit Correct answer.
  3. 100 degrees Fahrenheit
  4. 110 degrees Fahrenheit

Explanation

Lavatories in public facilities are typically limited to a maximum hot water delivery temperature of 120 degrees Fahrenheit to reduce scald risk. Tempering valves are commonly used to achieve this.

Question 23General Plumbing Knowledge

What is the purpose of an indirect waste receptor?

  1. To store hot water for the building
  2. To provide a vent for the building drain
  3. To receive waste from fixtures that must not connect directly to the drainage system Correct answer.
  4. To reduce water pressure in the distribution system

Explanation

An indirect waste receptor receives discharge from fixtures such as food service equipment that must be separated from the drainage system by an air gap. This prevents contamination of the drainage system.

Question 24General Plumbing Knowledge

A 2-inch horizontal drainage pipe is installed. What is the minimum slope required?

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

Explanation

A 2-inch horizontal drain must be installed at a minimum slope of 1/4 inch per foot to maintain adequate velocity. The 1/8 inch slope applies only to pipes 4 inches and larger.

Question 25General Plumbing Knowledge

What is the minimum required distance between a water service pipe and a building sewer where they run parallel underground?

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

Explanation

The code requires a minimum horizontal separation of 10 feet between a water service pipe and a building sewer running parallel underground. This prevents contamination of the potable supply.

Question 26General Plumbing Knowledge

A plumbing vent stack terminates above the roof. What is the minimum required height of the vent terminal above the roof surface when the roof is not used for any purpose other than weather protection?

  1. 12 inches Correct answer.
  2. 6 inches
  3. 24 inches
  4. 18 inches

Explanation

The plumbing code requires vent terminals to extend at least 12 inches above a roof that is not used for any purpose other than weather protection. This height helps prevent snow accumulation from blocking the vent and allows proper dispersion of sewer gases. Greater heights are required for roofs used as decks or where snow depth is significant.

Question 27General Plumbing Knowledge

A water closet is installed in a public restroom. What is the maximum water consumption per flush allowed for a water closet in a public facility?

  1. 1.28 gallons
  2. 3.5 gallons
  3. 1.6 gallons Correct answer.
  4. 1.0 gallon

Explanation

The maximum flush volume for a water closet in a public restroom is 1.6 gallons per flush under the Energy Policy Act and adopted plumbing codes. This standard applies to tanks and flushometer valves. Lower volumes such as 1.28 gallons are permitted but not required.

Question 28General Plumbing Knowledge

A horizontal drainage pipe is installed with a slope that is too steep. Which problem is most likely to occur in the drainage system?

  1. The trap seal will be siphoned because the flow velocity is too high.
  2. The water will drain too slowly and cause backup.
  3. The vent system will become pressurized.
  4. The pipe will clog more frequently because solids will settle out. Correct answer.

Explanation

When a horizontal drain is sloped too steeply, the liquid flows faster than the solids, leaving solids behind to accumulate and clog the pipe. Codes therefore limit the maximum slope of horizontal drainage pipes to prevent this separation. A uniform slope within the allowed range keeps solids moving with the flow.

Question 29General Plumbing Knowledge

A plumbing system is being tested with water. What is the minimum hydrostatic test pressure required for the water distribution piping system?

  1. 75 psi
  2. 50 psi
  3. 150 psi
  4. 100 psi Correct answer.

Explanation

The water distribution system must be tested hydrostatically at a pressure of at least 100 psi for a period of time specified by the code, typically one hour. This pressure exceeds normal working pressure and reveals leaks in joints and fittings. The test pressure must not be less than the working pressure of the system.

Question 30General Plumbing Knowledge

A 3-inch horizontal drainage pipe is installed. What is the minimum slope required for this pipe?

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

Explanation

For horizontal drainage pipes 3 inches and larger, the minimum slope is 1/8 inch per foot. Smaller pipes generally require 1/4 inch per foot. The slope must be uniform and sufficient to carry solids without clogging.

Question 31General Plumbing Knowledge

A water heater is installed in a garage. What is the minimum height above the floor at which the ignition source of a fuel-fired water heater must be elevated to protect against flammable vapors?

  1. 12 inches
  2. 6 inches
  3. 24 inches
  4. 18 inches Correct answer.

Explanation

Fuel-fired water heaters installed in garages must have the ignition source elevated at least 18 inches above the floor to reduce the risk of igniting gasoline vapors. This requirement applies to appliances with pilot lights or other ignition sources. Some codes allow alternative protection methods, but 18 inches is the standard.

Question 32General Plumbing Knowledge

A 2-inch vent pipe passes through a roof in an area subject to freezing temperatures. What is the minimum required size of the vent terminal?

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

Explanation

The vent terminal must be at least the same size as the vent pipe it serves, so a 2-inch vent requires a 2-inch terminal. In freezing climates, the terminal may need to be increased in size to prevent frost closure, but the minimum is the pipe size. A smaller terminal would restrict flow and increase the risk of blockage.

Question 33General Plumbing Knowledge

A horizontal branch serves a lavatory and connects to a vertical stack. What fitting is required at the connection to prevent wastewater from backing up into the branch?

  1. Wye branch
  2. Double sanitary tee
  3. Sanitary tee Correct answer.
  4. Test tee

Explanation

A sanitary tee is required for a horizontal branch connecting to a vertical stack because its curved pattern directs flow downward and reduces the chance of backup into the branch. Other fittings like wyes are used for horizontal-to-horizontal connections or where flow direction requires a gentler turn. The sanitary tee is specifically designed for vertical-to-horizontal drainage.

Question 34General Plumbing Knowledge

A floor drain is installed in a commercial kitchen. What is the minimum required size of the trap serving the floor drain?

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

Explanation

Floor drains in commercial kitchens must have a trap of at least 2 inches in diameter to handle the expected flow and waste. Larger traps are required for some fixtures, but 2 inches is the minimum for a floor drain. The trap must also be sized to match the drain outlet and the branch.

Question 35General Plumbing Knowledge

A backflow preventer is installed on a boiler feed line connected to the potable water supply. Which type of device provides the required protection against backflow?

  1. Reduced pressure principle backflow preventer Correct answer.
  2. Atmospheric vacuum breaker
  3. Air gap
  4. Pressure vacuum breaker

Explanation

A reduced pressure principle backflow preventer is required for boiler feed lines because it provides protection against both backpressure and backsiphonage, which are possible in a boiler system. Atmospheric and pressure vacuum breakers protect only against backsiphonage and are not suitable for continuous pressure applications. An air gap is not practical for a boiler feed line.

Question 36General Plumbing Knowledge

A plumbing system includes a sump pump that discharges groundwater. What is the minimum required size of the discharge pipe from the sump pump?

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

Explanation

The discharge pipe from a sump pump must be at least 1-1/4 inches in diameter to handle the pump's flow rate and reduce friction loss. Smaller sizes may not carry the volume and can cause the pump to overwork. Local codes may require larger sizes based on pump capacity.

Question 37General Plumbing Knowledge

A water service pipe is installed underground. What is the minimum required cover over the pipe where it passes under a driveway?

  1. 18 inches Correct answer.
  2. 30 inches
  3. 24 inches
  4. 12 inches

Explanation

Water service pipes under driveways require a minimum cover of 18 inches to protect against frost and physical damage from traffic loads. Greater depths may be required in colder climates. The cover is measured from the top of the pipe to the finished grade.

Question 38General Plumbing Knowledge

A plumbing fixture is installed in a location where the drainage system is subject to backflow. What is the minimum required air gap for a fixture with a 1-inch supply outlet?

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

Explanation

The minimum air gap for a fixture is twice the effective opening of the outlet, so a 1-inch outlet requires a 1-inch air gap. This gap prevents backflow by providing a physical separation between the supply and the fixture. The gap must be at least 1 inch regardless of outlet size.

Question 39General Plumbing Knowledge

A building has a 4-inch building sewer. What is the minimum slope required for the building sewer?

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

Explanation

Building sewers 4 inches and larger may be installed at a minimum slope of 1/8 inch per foot, provided the slope produces a velocity sufficient to carry solids. Smaller building sewers require 1/4 inch per foot. The slope must be uniform and approved by the authority having jurisdiction.

Question 40General Plumbing Knowledge

A plumbing system includes a 3-inch vent stack that extends through a roof. What is the minimum required size of the vent terminal?

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

Explanation

The vent terminal must be at least the same size as the vent pipe it serves, so a 3-inch vent stack requires a 3-inch terminal. In areas with heavy snow, the terminal may need to be larger to prevent closure by frost. A smaller terminal would restrict the vent and could cause pressure imbalances.

Question 41Plumbing Fixtures and Fixture Fittings

A water closet is installed in a public restroom. What is the minimum fixture clearance required from the centerline of the water closet to any side wall?

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

Explanation

Codes require a minimum of 15 inches of clear space measured from the centerline of a water closet to any side wall or partition. This dimension provides usable shoulder and elbow room for the user. A tighter spacing would render the fixture impractical and noncompliant.

Question 42Plumbing Fixtures and Fixture Fittings

What is the minimum unobstructed distance required from the front of a water closet to any wall or obstruction?

  1. 30 inches
  2. 24 inches
  3. 21 inches Correct answer.
  4. 18 inches

Explanation

Under New Hampshire's 2021 IPC/IBC framework, the ordinary minimum clearance from the front of a water closet to any wall or obstruction is 21 inches. Additional accessibility requirements may call for more space, but they do not make 24 inches the general minimum.

Question 43Plumbing Fixtures and Fixture Fittings

Which type of fixture trap is prohibited and uses water held around an inverted bell to form its seal?

  1. S-trap
  2. Drum trap
  3. P-trap
  4. Bell trap Correct answer.

Explanation

A bell trap forms its water seal with water held around an inverted bell. It is a prohibited fixture trap. Its distinctive bell-shaped construction, rather than an absence of water, identifies this trap.

Question 44Plumbing Fixtures and Fixture Fittings

A lavatory trap has a vertical distance of 30 inches between the trap outlet and the vent connection. Which statement is correct?

  1. The trap arm must be increased to at least 36 inches
  2. The trap arm is acceptable because horizontal distance governs
  3. The trap arm is excessive and must be re-vented Correct answer.
  4. The trap arm is acceptable because the fixture is a lavatory

Explanation

The vertical distance from a trap outlet to its vent is limited by code, typically to 24 inches for most fixtures. Exceeding this limit risks self-siphoning of the trap seal. The installation must be re-vented to bring the vent within the allowed distance.

Question 45Plumbing Fixtures and Fixture Fittings

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

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

Explanation

Fixture traps must maintain a water seal of at least 2 inches and not more than 4 inches. The 2-inch minimum resists evaporation and pressure fluctuations. A shallower seal would be prone to breaking under normal use.

Question 46Plumbing Fixtures and Fixture Fittings

An accessible lavatory is being installed in a commercial restroom. What is the maximum height of the lavatory rim above the finished floor?

  1. 36 inches
  2. 34 inches Correct answer.
  3. 32 inches
  4. 30 inches

Explanation

Accessibility standards require the lavatory rim to be no higher than 34 inches above the finished floor. This allows a person using a wheelchair to reach the basin and controls. Higher rims would restrict access.

Question 47Plumbing Fixtures and Fixture Fittings

What minimum clearance is required beneath an accessible lavatory to allow forward approach by a wheelchair?

  1. 24 inches
  2. 29 inches Correct answer.
  3. 27 inches
  4. 30 inches

Explanation

Accessible lavatories must provide at least 29 inches of clear knee clearance beneath the apron. This dimension allows a wheelchair user to pull forward to the basin. Lower clearances block the approach.

Question 48Plumbing Fixtures and Fixture Fittings

Which fixture is required to receive the discharge from a clothes washer in a residential installation?

  1. A laundry tray or standpipe Correct answer.
  2. A water closet
  3. A lavatory
  4. A floor drain

Explanation

A clothes washer must discharge through an indirect waste into a laundry tray or an approved standpipe. This arrangement prevents backflow and allows the washer hose to drain freely. Direct connection to a drain is not permitted.

Question 49Plumbing Fixtures and Fixture Fittings

A drinking fountain is installed in a public building. Which requirement applies to its waste connection?

  1. It must connect to a soil stack
  2. It may drain directly to the building drain
  3. It must discharge through an air gap or air break Correct answer.
  4. It may discharge into a floor drain without an air gap

Explanation

Drinking fountains are fixtures that handle potable water and must be protected against backflow. Their waste must discharge through an approved air gap or air break. This prevents contamination of the potable supply.

Question 50Plumbing Fixtures and Fixture Fittings

What is the minimum trap arm length, measured from the trap weir to the vent, for a 1-1/4 inch lavatory trap?

  1. 42 inches
  2. 72 inches
  3. 30 inches Correct answer.
  4. 60 inches

Explanation

The developed length of a trap arm is limited by the trap size to prevent self-siphoning. For a 1-1/4 inch trap, the maximum developed length to the vent is typically 30 inches. Longer arms risk losing the trap seal.