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NCCER Plumbing practice questions

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Question 1Plumbing (journey-level craft knowledge and skills)

What is the minimum required slope for a 3-inch diameter horizontal drainage pipe under the International Plumbing Code?

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

Explanation

The IPC requires drainage piping 3 inches and larger to slope at least 1/8 inch per foot, while pipe 2 1/2 inches and smaller must slope at least 1/4 inch per foot. The larger pipe carries more flow, so a gentler grade still maintains self-cleansing velocity.

Question 2Plumbing (journey-level craft knowledge and skills)

A plumbing fixture that discharges into the drainage system must be protected against backflow and sewer gas by which component installed between the fixture and the trap?

  1. A vent
  2. A trap Correct answer.
  3. A cleanout
  4. A water hammer arrestor

Explanation

Every fixture connected to the drainage system requires a water seal trap to prevent sewer gas from entering the building. The trap holds a water seal of 2 to 4 inches that blocks gas while allowing wastewater to pass.

Question 3Plumbing (journey-level craft knowledge and skills)

When soldering copper tube, what is the primary purpose of applying flux to the cleaned tube end and fitting socket?

  1. To raise the melting point of the solder
  2. To act as a permanent sealant after the joint cools
  3. To chemically clean the surfaces and exclude oxygen so solder can flow Correct answer.
  4. To prevent the solder from entering the joint

Explanation

Flux removes oxides and shields the heated metal from air so capillary action can draw solder into the joint. Without flux, oxidation prevents proper solder flow and weakens the connection.

Question 4Plumbing (journey-level craft knowledge and skills)

What is the standard pressure rating used when sizing a water distribution system for a single-family dwelling served by a typical municipal main?

  1. 150 psi
  2. 80 psi Correct answer.
  3. 40 psi
  4. 20 psi

Explanation

Water distribution sizing commonly assumes a static pressure of about 80 psi at the meter for residential service, then deducts friction and elevation losses to each fixture. Sizing tables use this baseline to ensure adequate residual pressure at the farthest fixture.

Question 5Plumbing (journey-level craft knowledge and skills)

Which material is typically joined using a solvent cement and primer?

  1. PVC plastic pipe Correct answer.
  2. PEX tubing
  3. Cast iron soil pipe
  4. Galvanized steel pipe

Explanation

PVC and CPVC plastic pipe are joined with solvent cement after applying primer to soften and clean the surfaces. The cement welds the pipe and fitting into a continuous plastic joint.

Question 6Plumbing (journey-level craft knowledge and skills)

What is the minimum size of a building drain serving a single-family dwelling with one bathroom group?

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

Explanation

The building drain of a dwelling must be at least 3 inches in diameter to carry the combined discharge of the fixtures and maintain adequate slope. Smaller sizes are permitted only for individual fixture branches.

Question 7Plumbing (journey-level craft knowledge and skills)

A water closet is being installed in a public restroom. What is the minimum water closet compartment width required by the IPC for a floor-mounted fixture?

  1. 48 inches
  2. 30 inches Correct answer.
  3. 24 inches
  4. 36 inches

Explanation

The IPC requires a minimum 30-inch clear width for a water closet compartment in public facilities. This width provides adequate space for use and access.

Question 8Plumbing (journey-level craft knowledge and skills)

Which tool is used to cut internal threads on the end of a steel pipe?

  1. A flaring tool
  2. A pipe die Correct answer.
  3. A pipe reamer
  4. A pipe cutter

Explanation

A pipe die cuts external threads on steel pipe so it can be joined to threaded fittings. The die is turned onto the pipe end, progressively cutting the tapered threads.

Question 9Plumbing (journey-level craft knowledge and skills)

A vent stack serving a 4-inch soil stack in a 10-story building must extend how far above the roof?

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

Explanation

Vent terminals must extend at least 6 inches above the roof, but where the roof is used for other purposes or where snow accumulation is a factor, the vent must extend higher. For a building of this height, the vent must extend at least 12 inches above the roof surface to clear snow and prevent blockage.

Question 10Plumbing (journey-level craft knowledge and skills)

A lavatory drain is 1 1/4 inches in diameter. What is the minimum trap arm length permitted before the vent connection?

  1. No limit
  2. The distance equal to twice the pipe diameter
  3. The distance equal to the developed length of the trap arm based on slope Correct answer.
  4. The distance equal to the pipe diameter

Explanation

The trap arm length is limited by the slope of the pipe and the diameter so that the water seal is not broken by back pressure. The maximum developed length is determined by the pipe diameter and slope, typically from code tables.

Question 11Plumbing (journey-level craft knowledge and skills)

A plumbing system requires a 2-inch vent through a roof. What is the minimum distance the vent must be from an operable window?

  1. 5 feet
  2. No minimum distance
  3. 10 feet Correct answer.
  4. 3 feet

Explanation

Vent terminals must be located at least 10 feet from any operable window, door, or air intake to prevent sewer gas from entering the building. This distance protects occupants from noxious fumes.

Question 12Plumbing (journey-level craft knowledge and skills)

A water heater is installed in a garage. What is the minimum height above the floor at which the ignition source must be located?

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

Explanation

In a garage, the ignition source of a fuel-fired water heater must be at least 18 inches above the floor to reduce the risk of igniting gasoline vapors, which are heavier than air. This requirement is intended to prevent fires and explosions.

Question 13Plumbing (journey-level craft knowledge and skills)

A 3-inch horizontal drain pipe runs 20 feet at 1/4 inch per foot. What is the total fall along this run?

  1. 5 inches Correct answer.
  2. 2 1/2 inches
  3. 10 inches
  4. 20 inches

Explanation

Total fall is the slope multiplied by the run length. One-quarter inch per foot times 20 feet equals 5 inches of fall.

Question 14Plumbing (journey-level craft knowledge and skills)

When installing a PEX water distribution system, what is the purpose of a manifold?

  1. To distribute hot and cold water to individual fixtures from a central location Correct answer.
  2. To filter sediment from the water supply
  3. To provide a trap for each fixture
  4. To reduce water pressure

Explanation

A manifold is a central distribution point that splits the main supply into individual lines to each fixture, reducing fittings and allowing independent shutoff. This design also minimizes pressure loss and simplifies repairs.

Question 15Plumbing (journey-level craft knowledge and skills)

A backflow prevention device is required on a hose bibb in a commercial building. What type of device is typically used?

  1. A check valve
  2. A pressure-relief valve
  3. A vacuum breaker Correct answer.
  4. A trap primer

Explanation

A hose bibb in a commercial setting requires a vacuum breaker to prevent backflow of contaminated water into the potable supply. The vacuum breaker opens to atmosphere when pressure drops, breaking the siphon.

Question 16Plumbing (journey-level craft knowledge and skills)

What is the minimum size for a cleanout opening on a 4-inch building drain?

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

Explanation

A cleanout must be the same size as the pipe it serves, so a 4-inch building drain requires a 4-inch cleanout. This allows full access for clearing blockages.

Question 17Plumbing (journey-level craft knowledge and skills)

A lavatory faucet is being installed. What is the required flow rate for a residential lavatory faucet under current standards?

  1. 2.2 gallons per minute
  2. 1.5 gallons per minute Correct answer.
  3. 1.2 gallons per minute
  4. 2.5 gallons per minute

Explanation

Current federal standards limit residential lavatory faucets to a maximum of 1.5 gallons per minute at 60 psi. This conserves water while maintaining adequate flow for handwashing.

Question 18Plumbing (journey-level craft knowledge and skills)

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

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

Explanation

The water distribution system must be tested at a pressure of at least 100 psi for a specified duration to verify there are no leaks. This pressure exceeds normal operating pressure and reveals weak joints.

Question 19Plumbing (journey-level craft knowledge and skills)

A drainage fixture unit (dfu) value is used to size which of the following?

  1. Drainage piping Correct answer.
  2. Water supply piping
  3. Gas piping
  4. Vent terminal height

Explanation

Drainage fixture units quantify the probable discharge load of fixtures and are used to size drainage piping and vents. Each fixture is assigned a dfu value based on its discharge characteristics.

Question 20Plumbing (journey-level craft knowledge and skills)

A 4-inch horizontal soil drain receives a 3-inch horizontal water closet branch at a right-angle junction. What fitting should be used at this connection to direct flow downstream?

  1. A sanitary tee
  2. A double sanitary tee
  3. A vent tee
  4. A wye with a 45-degree bend Correct answer.

Explanation

For a horizontal branch entering a horizontal drain at a right-angle junction, a wye with a 45-degree bend provides a sweeping drainage connection that directs flow downstream. A sanitary tee is generally permitted for horizontal-to-vertical drainage connections, but not for this horizontal-to-horizontal configuration.

Question 21Plumbing (journey-level craft knowledge and skills)

A building has a 6-inch building drain at 1/8 inch per foot slope and a 4-inch branch at 1/4 inch per foot. Which statement about the flow capacity is correct?

  1. The 6-inch drain carries more flow because of its larger diameter despite the gentler slope Correct answer.
  2. The 6-inch drain carries less flow because the slope is too shallow
  3. The 4-inch branch carries more flow than the 6-inch drain because of its steeper slope
  4. Both pipes carry equal flow because the slope compensates for diameter

Explanation

Flow capacity in gravity drainage depends primarily on pipe diameter and slope. The larger diameter of the 6-inch drain provides greater cross-sectional area and capacity even at the gentler 1/8 inch per foot slope, which is why larger pipes are allowed shallower grades.

Question 22Plumbing (journey-level craft knowledge and skills)

A vent stack is being installed for a 10-story building. Which condition requires an increase in the vent size?

  1. The vent stack is installed in an exterior wall
  2. The vent stack is less than 40 feet tall
  3. The vent stack is offset more than 45 degrees Correct answer.
  4. The vent stack serves more than one fixture

Explanation

When a vent stack is offset more than 45 degrees, the offset must be sized as a vent stack and may require an increase in size to maintain proper venting. Offsets change the pressure characteristics and can cause the vent to function improperly if undersized.

Question 23Plumbing (journey-level craft knowledge and skills)

A water heater is being installed with a temperature and pressure relief valve. Where must the discharge pipe terminate?

  1. In a concealed location inside a wall
  2. Directly into the drainage system without an air gap
  3. At a height of 12 inches above the floor
  4. Within 6 inches of the floor or to the outside Correct answer.

Explanation

The T&P relief valve discharge must terminate within 6 inches of the floor or outside the building, with no threading or trapping, to prevent scalding and allow free discharge. This location ensures safe release of hot water and steam.

Question 24Plumbing (journey-level craft knowledge and skills)

A plumbing system has a 3-inch drain with a 1/8 inch per foot slope. What is the approximate velocity of flow when the pipe is flowing full, assuming a roughness coefficient that gives a hydraulic radius of 0.75 inches?

  1. 8 feet per second
  2. 1 foot per second
  3. 4 feet per second
  4. 2 feet per second Correct answer.

Explanation

Using Manning's equation with a hydraulic radius of 0.75 inches and a slope of 1/8 inch per foot, the velocity is approximately 2 feet per second. This velocity is near the self-cleansing threshold for drainage piping.

Question 25Plumbing (journey-level craft knowledge and skills)

A plumbing inspector finds a 2-inch vent pipe passing through a roof in an area subject to heavy snow. What is the minimum height above the roof required?

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

Explanation

Where snow accumulation is a factor, the vent must extend at least 24 inches above the roof to prevent blockage by snow. The standard 6-inch minimum is insufficient in snow-prone areas.

Question 26Plumbing (journey-level craft knowledge and skills)

A plumber is joining two lengths of copper tubing in a potable water line using a lead-free solder. Which filler metal and flux combination is appropriate for this joint?

  1. 50/50 tin-lead solder with acid-paste flux
  2. Lead-free solder with self-cleaning flux approved for potable water Correct answer.
  3. 95/5 tin-antimony solder with water-soluble flux
  4. Silver brazing alloy with borax flux only

Explanation

Potable water joints require lead-free solder and a flux rated for the application; self-cleaning fluxes are acceptable when listed for potable use. The flux must be compatible with the filler and must be cleaned from the joint to prevent corrosion. Selecting a listed combination ensures the joint meets code and health requirements.

Question 27Plumbing (journey-level craft knowledge and skills)

A plumber is installing a floor drain in a commercial kitchen. Which feature is required to prevent sewer gases from entering the building?

  1. A backwater valve on the branch
  2. A trap with a liquid seal of the required depth Correct answer.
  3. A trap primer connected to the domestic water line
  4. A vent cap on the drain body

Explanation

Every floor drain must be trapped, and the trap must maintain a liquid seal of the depth required by code, typically 2 to 4 inches. The seal blocks sewer gas from entering the space. Trap primers help maintain the seal but do not replace the trap itself.

Question 28Plumbing (journey-level craft knowledge and skills)

A plumber is sizing a water service for a building with a known fixture unit count and a required residual pressure. Which factor most directly determines the pipe size selected from the sizing tables?

  1. The building's total floor area
  2. The developed length of the piping plus equivalent length of fittings Correct answer.
  3. The number of water heaters installed
  4. The diameter of the building drain

Explanation

Water supply sizing depends on the demand in fixture units, the available pressure, and the total equivalent length of pipe and fittings. The developed length plus fitting allowances determines friction loss, which drives the required diameter. Floor area, water heater count, and drain size do not set supply pipe size.

Question 29Plumbing (journey-level craft knowledge and skills)

A plumber must support a horizontal run of 4-inch cast-iron soil pipe. What is the maximum spacing between supports for this pipe?

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

Explanation

Cast-iron soil pipe in horizontal runs is typically supported at intervals not exceeding 10 feet, with a support near each joint and at changes in direction. Closer spacing is required for smaller diameters and for some hanger types. Exceeding the spacing allows sag and joint stress.

Question 30Plumbing (journey-level craft knowledge and skills)

A plumber is installing a water closet in a public restroom. Which dimension is regulated to ensure proper clearance in front of the fixture?

  1. The length of the supply stop
  2. The diameter of the closet flange
  3. The height of the flush valve above the bowl
  4. The clearance from the front of the bowl to the wall or obstruction Correct answer.

Explanation

Accessibility standards set a minimum clearance in front of a water closet so a wheelchair can approach and transfer. The distance from the front of the bowl to the opposite wall or obstruction is the regulated dimension. Flush valve height, flange diameter, and supply stop length are not the governing clearance.

Question 31Plumbing (journey-level craft knowledge and skills)

A plumber is installing a horizontal branch in a drainage system. Which condition requires the branch to be vented?

  1. When the branch serves a fixture with a 1 1/2-inch trap
  2. When the trap arm exceeds the allowable developed length for its diameter Correct answer.
  3. When the branch carries more than two fixture units
  4. When the branch is installed below a concrete slab

Explanation

A trap arm must connect to a vent within the maximum developed length permitted for its diameter, or the trap seal can be siphoned. When that distance is exceeded, a vent must be added. The other conditions do not by themselves trigger a vent requirement.

Question 32Plumbing (journey-level craft knowledge and skills)

A plumber is pressure-testing a new DWV system with water. Which practice is correct?

  1. Fill the system and test at a pressure equal to the building's water supply pressure
  2. Fill the system and test at a minimum of 10 feet of head above the highest point Correct answer.
  3. Test each fixture individually without filling the piping
  4. Test with compressed air only

Explanation

A water test of a DWV system requires filling the piping and maintaining a head of at least 10 feet above the highest point of the section under test. The system is then inspected for leaks. Air testing is allowed only where water testing is impractical and where approved.

Question 33Plumbing (journey-level craft knowledge and skills)

A plumber is installing a sump pump in a basement. Which installation practice helps prevent the pump from cycling too frequently?

  1. Setting the pump on the basin floor without a stand
  2. Reducing the discharge pipe diameter
  3. Installing a check valve on the discharge line Correct answer.
  4. Removing the float switch

Explanation

A check valve on the discharge line keeps water in the pipe from draining back into the basin after the pump shuts off, which reduces short cycling. The basin should also have adequate volume so the pump runs long enough between cycles. Pump stands and float settings also affect cycling.

Question 34Plumbing (journey-level craft knowledge and skills)

A plumber is installing a reduced-pressure principle backflow preventer on a domestic water line. Which condition is required for this device?

  1. It must be protected from freezing and provided with adequate drainage for relief discharge Correct answer.
  2. It must be installed below grade in a vault
  3. It must be installed downstream of every fixture
  4. It must be tested only at initial installation

Explanation

An RPZ device discharges water from its relief port during a pressure reversal, so it must be protected from freezing and located where discharge can drain safely. It must also be tested at installation and at required intervals thereafter. Installation below grade is permitted only in a properly drained vault.

Question 35Plumbing (journey-level craft knowledge and skills)

A plumber is installing a gas-fired water heater in a confined space. Which provision supplies combustion air?

  1. A sealed room with no openings
  2. A single opening at ceiling height only
  3. Two permanent openings sized to the required free area Correct answer.
  4. An opening sized to the flue diameter

Explanation

Confined spaces require combustion air supplied through permanent openings sized by the appliance input rating. Two openings, one near the floor and one near the ceiling, are the standard arrangement. A sealed room starves the appliance of air and creates a hazard.

Question 36Plumbing (journey-level craft knowledge and skills)

A plumber is installing a lavatory drain with a 1 1/4-inch trap arm. What is the maximum developed length of the trap arm before a vent is required?

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

Explanation

The maximum developed length of a trap arm depends on its diameter; for a 1 1/4-inch trap arm the limit is commonly 2 feet 6 inches. The trap arm must also slope so the trap weir is not above the vent connection. Exceeding the length risks siphonage of the trap seal.

Question 37Plumbing (journey-level craft knowledge and skills)

A plumber is installing a fixture drain that connects to a horizontal branch. Which fitting is used where the drain changes from vertical to horizontal?

  1. A sanitary tee
  2. A long-turn quarter bend Correct answer.
  3. A street 45
  4. A double sanitary tee

Explanation

Where a vertical drain turns to horizontal, a long-turn fitting or a combination wye and eighth bend is used to provide a smooth flow path. A sanitary tee is intended for horizontal-to-vertical changes. Sharp bends cause solids to settle and clog.

Question 38Plumbing (journey-level craft knowledge and skills)

A plumber is installing a water distribution system using PEX tubing. Which practice protects the tubing from damage where it passes through framing?

  1. Supporting the tubing only at the ends of the run
  2. Using nail plates or protective sleeves where required Correct answer.
  3. Fastening the tubing tightly against the stud
  4. Running the tubing through the same hole as the electrical cable

Explanation

PEX must be protected from nails and screws where it passes through framing members, using nail plates or sleeves as required. The tubing also needs support at intervals and must be isolated from heat sources and abrasion. Tight fastening can crush the tubing and restrict flow.

Question 39Plumbing (journey-level craft knowledge and skills)

A plumber is installing a grease interceptor for a restaurant. Which practice is correct?

  1. Route sanitary waste from restrooms through the interceptor
  2. Install the interceptor downstream of the building drain
  3. Bypass the interceptor during peak hours
  4. Connect the kitchen sink and dishwasher drain to the interceptor Correct answer.

Explanation

A grease interceptor receives only the waste that carries fats, oils, and grease, typically from kitchen sinks and dishwashers. Sanitary waste must bypass it to avoid odor and overload. The interceptor is installed close to the fixtures it serves, ahead of the building drain.

Question 40Plumbing (journey-level craft knowledge and skills)

A plumber is installing a bidet in a commercial restroom. Which backflow protection is typically required for the fixture supply?

  1. An air gap or a vacuum breaker Correct answer.
  2. A check valve only
  3. A water hammer arrestor
  4. A pressure-reducing valve

Explanation

Bidet supplies can be submerged or cross-connected, so they require an air gap or an approved vacuum breaker to protect the potable supply. A check valve alone is not sufficient protection against backflow. Pressure-reducing valves and arrestors serve other purposes.

Question 41Plumbing (journey-level craft knowledge and skills)

A plumber is installing a water heater with a temperature and pressure relief valve. Which installation detail is correct?

  1. Install the valve on the cold inlet only
  2. Cap the relief valve discharge to prevent drips
  3. Route the discharge to a safe point of disposal with no trap Correct answer.
  4. Reduce the discharge pipe size to fit the drain

Explanation

The T&P relief valve discharge must be piped full size to a safe point of disposal, such as a floor drain or outside, without a trap or cap. Trapping or capping the discharge can cause a pressure buildup and a dangerous failure. The valve is mounted on the tank as specified by the manufacturer.

Question 42Plumbing (journey-level craft knowledge and skills)

A plumber is installing a cleanout at the base of a stack. Which requirement applies to the cleanout?

  1. It must be the same size as the stack and accessible Correct answer.
  2. It must be installed only at the top of the stack
  3. It must be smaller than the stack to increase velocity
  4. It must be concealed behind a finished wall

Explanation

A cleanout at the base of a stack must be full size, equal to the pipe it serves, and must remain accessible for maintenance. Concealing it defeats its purpose. Cleanouts are also required at other locations, such as the end of horizontal runs.

Question 43Plumbing (journey-level craft knowledge and skills)

A plumber is installing a storm drainage system. Which statement about roof drains is correct?

  1. Roof drains may connect to the sanitary sewer without approval
  2. Roof drains must discharge to a storm system or approved point of disposal Correct answer.
  3. Roof drains must be vented through the roof
  4. Roof drains require a trap primer

Explanation

Storm water from roof drains must go to a storm drainage system or another approved point of disposal, not to the sanitary sewer unless specifically approved. Roof drains are typically trapped and may need protection against freezing. They are not vented through the roof like soil stacks.

Question 44Plumbing (journey-level craft knowledge and skills)

A plumber is installing a water service line and must protect it from frost. Which method is acceptable?

  1. Insulate the line and leave it at grade
  2. Drain the line each night
  3. Bury the line below the local frost depth Correct answer.
  4. Install a heat trace cable without burial

Explanation

The service line must be buried below the frost depth established for the area, or otherwise protected by an approved method. Insulation alone does not prevent freezing in prolonged cold. Heat tracing may be used but does not replace proper burial where required.

Question 45Plumbing (journey-level craft knowledge and skills)

A plumber is installing a fixture that requires a 2-inch trap. Which statement about the trap is correct?

  1. The trap must be a water-seal trap with a smooth interior Correct answer.
  2. The trap may be a bell trap
  3. The trap may be double-trapped
  4. The trap may have a removable bottom for cleaning

Explanation

Traps must be water-seal traps with smooth interiors that resist the accumulation of waste. Bell traps and traps with moving parts are prohibited. Double trapping is not permitted because it can cause air lock and erratic drainage.

Question 46Plumbing (journey-level craft knowledge and skills)

A plumber is installing a 3-inch horizontal drain that runs 12 feet at 1/4 inch per foot. What is the total fall over the run?

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

Explanation

Total fall equals the slope multiplied by the run: 1/4 inch per foot times 12 feet equals 3 inches. The fall must be maintained uniformly along the run. Insufficient fall allows solids to settle, while excessive fall can leave liquids behind.

Question 47Plumbing (journey-level craft knowledge and skills)

A plumber is installing a vent terminal on a roof. Which condition requires the vent to be increased in size or relocated?

  1. The vent is installed on a flat roof
  2. The vent is located near a window that can be opened Correct answer.
  3. The vent is made of PVC
  4. The vent is 12 inches above the roof surface

Explanation

A vent terminal near an operable window, door, or air intake can allow sewer gas to enter the building, so it must be relocated or the vent extended. Vent terminals must also meet height requirements above the roof. Material and roof type alone do not trigger a size increase.

Question 48Plumbing (journey-level craft knowledge and skills)

A plumber is installing a lavatory faucet in a public restroom. Which feature is required to limit the water temperature at the fixture?

  1. A pressure-reducing valve
  2. A flow restrictor
  3. A vacuum breaker
  4. A tempering valve or thermostatic mixing valve Correct answer.

Explanation

Public lavatories require a means to limit hot water temperature at the fixture to prevent scalding, typically a tempering or thermostatic mixing valve. Pressure-reducing valves control supply pressure, and vacuum breakers protect against backflow. Flow restrictors limit volume, not temperature.

Question 49Plumbing (journey-level craft knowledge and skills)

A plumber is installing a horizontal wet vent. Which condition must be met for the wet vent to be acceptable?

  1. The wet vent must be installed below the building drain
  2. The wet vent must serve fixtures in the same bathroom group and be sized for the total fixture units Correct answer.
  3. The wet vent must connect to a storm drain
  4. The wet vent must be at least 4 inches in diameter

Explanation

A horizontal wet vent is permitted when it serves fixtures in the same bathroom group and is sized for the fixture units it carries. It must also be installed with the required slope and connections. Oversizing or connecting to a storm drain is not the criterion.

Question 50Plumbing (journey-level craft knowledge and skills)

A plumber is installing a water hammer arrestor. Where is it best located?

  1. At the end of the branch near the quick-closing valve Correct answer.
  2. At the water meter only
  3. At the water heater inlet
  4. At the building drain

Explanation

Water hammer arrestors are most effective when installed close to the quick-closing valve that causes the surge, such as at the end of the branch serving a solenoid or flush valve. Locating them remotely reduces their effectiveness. They are not installed on drains.