Journeyman Plumber Exam — Questions and Answers

Question 1: Under IPC, what is the minimum distance a water closet centerline must be from a side wall or obstruction?

18 inches
12 inches
15 inches (Correct answer)
21 inches

Correct answer: 15 inches

The IPC requires a minimum of 15 inches from the water closet centerline to any side wall or obstruction.

Question 2: Which standard published by ASSE specifically covers reduced pressure zone backflow preventers?

ASSE 1001
ASSE 1020
ASSE 1035
ASSE 1013 (Correct answer)

Correct answer: ASSE 1013

ASSE 1013 is the performance standard for reduced pressure principle backflow preventers used in potable water systems.

Question 3: Which of the following backflow prevention devices is considered the most effective and simplest form, providing a physical separation between the potable water outlet and a potential contaminant?

Reduced Pressure Zone Assembly (RPZ)
Air Gap (Correct answer)
Double Check Valve Assembly (DCVA)
Pressure Vacuum Breaker (PVB)

Correct answer: Air Gap

An air gap is a physical separation between the free-flowing discharge end of a potable water supply pipe and the flood-level rim of a receptacle. It is the most reliable and simplest method of backflow prevention because there is no physical connection for contaminants to cross.

Question 4: What is the minimum slope for a horizontal wet vent pipe?

1/4 inch per foot (Correct answer)
1/2 inch per foot
No slope is required
1/8 inch per foot

Correct answer: 1/4 inch per foot

Horizontal wet vent pipes must slope at least 1/4 inch per foot toward the drain to maintain proper flow and self-scouring velocity.

Question 5: On an isometric drawing, which axis represents the vertical direction?

The horizontal right axis
The diagonal axis
The horizontal left axis
The vertical axis (Correct answer)

Correct answer: The vertical axis

The vertical axis on an isometric drawing represents the true vertical (up/down) direction of the piping system.

Question 6: The purpose of a sediment trap (drip leg) installed at a gas appliance is to:

Catch moisture and debris before they reach the appliance valve (Correct answer)
Increase gas pressure to the appliance
Regulate gas flow rate
Serve as a shutoff point during emergencies

Correct answer: Catch moisture and debris before they reach the appliance valve

A sediment trap collects condensate and pipe scale that would otherwise clog or damage the appliance's gas valve and controls.

Question 7: How often must a testable backflow prevention assembly be tested after installation?

Only at time of installation
Every 6 months
Annually (Correct answer)
Every 2 years

Correct answer: Annually

Most jurisdictions following the USC model require testable backflow prevention assemblies to be tested annually by a certified tester.

Question 8: Which type of backflow is caused by downstream pressure exceeding supply pressure?

Vapor lock backflow
Thermal expansion backflow
Back-siphonage
Back-pressure backflow (Correct answer)

Correct answer: Back-pressure backflow

Back-pressure backflow occurs when downstream pressure (from pumps, boilers, or elevated tanks) exceeds the supply pressure.

Question 9: What is a 'P-trap'?

A trap shaped like the letter P used for pressure balancing
A pressure-testing fitting used during inspection
A cleanout plug at the base of a vertical stack
A fixture trap with a water seal that prevents sewer gas entry (Correct answer)

Correct answer: A fixture trap with a water seal that prevents sewer gas entry

A P-trap is the standard fixture trap that maintains a water seal to prevent sewer gases from entering the building through fixture drains.

Question 10: What is the shortest possible distance that a department store employee should have to travel to use the restroom?

250 feet
500 feet (Correct answer)
375 feet
100 feet

Correct answer: 500 feet

The distance that employees must go to access appropriate bathroom facilities cannot exceed 500 feet. They won't have to climb more than one set of steps during this stroll. Under these circumstances, bathrooms cannot be built more than one floor above the workspace. Buildings that house factory or industrial workers may be exempt from this rule. The normal guideline is the 500-foot rule, but you should verify your local ordinance to make sure.

Question 11: What is the federally mandated maximum flow rate for a standard showerhead manufactured after 1994, according to the Energy Policy Act?

1.8 GPM at 80 psi
2.5 GPM at 80 psi (Correct answer)
2.0 GPM at 80 psi
3.0 GPM at 60 psi

Correct answer: 2.5 GPM at 80 psi

The U.S. Energy Policy Act of 1992 (effective 1994) set the national maximum flow rate for showerheads at 2.5 gallons per minute (GPM) when tested at a pressure of 80 pounds per square inch (psi). While some states and programs like WaterSense have adopted lower rates, 2.5 GPM remains the federal standard.

Question 12: A gas pipe run exposed in a garage must be protected from vehicle damage by:

Routing it at least 6 feet above the floor or installing mechanical protection (Correct answer)
Installing a pressure relief valve
Enclosing it in a conduit
Painting it yellow for visibility

Correct answer: Routing it at least 6 feet above the floor or installing mechanical protection

Gas piping in garages must either be installed at least 6 feet above the floor or protected by physical barriers to prevent damage from vehicles.

Question 13: Which of the following is the correct mathematical constant used to calculate the 'travel' piece when the 'set' of a 60-degree offset is known?

1.732
2.613
1.414
1.155 (Correct answer)

Correct answer: 1.155

The constant for calculating the travel of a 60-degree offset is 1.155. The formula is: Travel = Set x 1.155. The constant 1.414 is for 45-degree offsets, and 2.613 is for 22.5-degree offsets.

Question 14: Which of the following is an example of a high-hazard cross-connection?

A carbonated beverage dispenser connected to potable water (Correct answer)
A lawn sprinkler system with no fertilizer injection
A garden hose left in a bucket of soapy water
A water softener bypass line

Correct answer: A carbonated beverage dispenser connected to potable water

Carbonated beverage dispensers create a high-hazard cross-connection because CO2 and syrup can be siphoned back into the potable supply.

Question 15: Under the IPC, what is the maximum number of fixture units permitted on a 3-inch horizontal branch drain sloped at 1/4 inch per foot?

30 DFUs
10 DFUs
20 DFUs (Correct answer)
42 DFUs

Correct answer: 20 DFUs

A 3-inch horizontal branch at 1/4-inch-per-foot slope can carry a maximum of 20 drainage fixture units per IPC Table 710.1(2).

Question 16: What is the correct procedure when a gas leak is suspected in a building?

Shut off the gas at the meter, evacuate, and call the gas company from outside (Correct answer)
Tighten all fittings while the gas is still on
Locate the leak with a flame before evacuating
Open windows and use an electric fan to ventilate the area

Correct answer: Shut off the gas at the meter, evacuate, and call the gas company from outside

When a gas leak is suspected, the correct response is to shut off gas at the meter, evacuate all occupants, avoid any ignition sources, and call the utility from outside the building.

Question 17: Which of the following is explicitly PROHIBITED by code for the discharge pipe of a water heater's Temperature and Pressure (T&P) relief valve?

Installing any type of shutoff valve or tee fitting in the line. (Correct answer)
Terminating the pipe 6 inches above a floor drain.
Constructing the pipe from approved materials like copper or CPVC.
Pitching the pipe downwards to allow for drainage by gravity.

Correct answer: Installing any type of shutoff valve or tee fitting in the line.

The discharge line from a T&P valve is a critical safety feature that must remain unobstructed at all times. Installing any valve, tee, or other potential obstruction is strictly prohibited by plumbing codes (IPC 504.6) as it could prevent the valve from relieving dangerous excess pressure or temperature.

Question 18: What is the flammability range (lower explosive limit to upper explosive limit) of natural gas in air?

15% to 25%
5% to 15% (Correct answer)
1% to 5%
20% to 50%

Correct answer: 5% to 15%

Natural gas is flammable when its concentration in air is between approximately 5% (LEL) and 15% (UEL); outside this range it will not ignite.

Question 19: Which venting arrangement is used when a vent pipe must be routed under a slab before it can rise to open air?

Install an AAV at the fixture instead
An engineered vent system approved by the AHJ (Correct answer)
This configuration is never permitted
A Chicago loop or return vent configuration

Correct answer: An engineered vent system approved by the AHJ

When a vent must pass under a slab, an engineered vent system specifically approved by the authority having jurisdiction (AHJ) is required.

Question 20: Under the IPC, what is the maximum distance a trap can be located from its vent?

6 feet
2 feet
10 feet for all pipe sizes
The distance depends on the pipe size and slope (Correct answer)

Correct answer: The distance depends on the pipe size and slope

The maximum trap-to-vent distance is determined by the pipe diameter — for example, 3.5 feet for a 1.25-inch pipe and 6 feet for a 2-inch pipe.

Question 21: A plumber is sizing a water service pipe for a single-family home using the Water Supply Fixture Unit (WSFU) method. The total WSFU load is 28, the developed length to the furthest fixture is 120 feet, and the static street pressure is 55 psi. Using a typical IPC/UPC sizing table, what is the minimum required size for the copper water service pipe?

1 inch (Correct answer)
1 1/4 inch
3/4 inch
1 1/2 inch

Correct answer: 1 inch

Based on typical plumbing code sizing tables (like those in the UPC or IPC), you would find the appropriate pressure range (e.g., 46-60 psi), then cross-reference the developed length column (e.g., 100-150 feet) with the WSFU load. For a load of 28 WSFU at that length and pressure, a 3/4" pipe is typically insufficient, making a 1-inch pipe the correct minimum size to maintain adequate pressure and flow.

Question 22: When connecting a clothes washer standpipe to the drainage system, the standpipe must extend at least how high above the trap?

18 inches
24 inches (Correct answer)
36 inches
12 inches

Correct answer: 24 inches

The IPC requires the clothes washer standpipe to extend at least 18 inches but not more than 42 inches above the trap.

Question 23: A plumber needs to connect a horizontal branch drain to a vertical stack. To ensure proper flow and prevent blockages, which type of fitting is most appropriate for this connection?

A vent tee
A short sweep 90-degree elbow
A sanitary tee
A combination wye and 1/8 bend or a long sweep fitting (Correct answer)

Correct answer: A combination wye and 1/8 bend or a long sweep fitting

When transitioning from a horizontal drain to a vertical stack, it is critical to use fittings that promote a smooth, sweeping change in direction. A combination wye and 1/8 bend (or a long sweep fitting) is required to prevent solids from building up at the change of direction, which can occur with the sharper turn of a sanitary tee. Sanitary tees are typically used for vertical to horizontal transitions.

Question 24: A plumber is performing a field test on a Reduced Pressure Principle (RP) backflow preventer (ASSE 1013). During the test of the relief valve, what is the minimum differential pressure at which the valve must begin to open and drip?

0.5 psid
5.0 psid
2.0 psid (Correct answer)
1.0 psid

Correct answer: 2.0 psid

According to the ASSE 1013 standard for Reduced Pressure Principle backflow prevention assemblies, the relief valve is a critical safety component. During a field test, it must open and begin to discharge water when the pressure differential between the check valves drops to 2.0 psid (pounds per square inch differential) or above. This ensures it will function correctly to prevent backflow.

Question 25: If a reduced pressure zone assembly's relief port is discharging continuously during normal system operation, this most likely indicates:

A failed or fouled check valve allowing pressure differential to drop below 2 psi (Correct answer)
The supply pressure is too high for the assembly rating
The device is functioning normally and expelling excess pressure
The downstream demand is exceeding supply pressure

Correct answer: A failed or fouled check valve allowing pressure differential to drop below 2 psi

Continuous discharge from the relief port indicates that the differential pressure across the first check has dropped below the 2 psi threshold, typically due to a failed or debris-fouled check valve.

Question 26: A plumber is sizing the water distribution system for a single-family residence. The municipal water main provides a static pressure of 95 psi at the property line. Which of the following is required?

A larger diameter service pipe
A backflow preventer
A water hammer arrestor at the meter
A pressure reducing valve (PRV) (Correct answer)

Correct answer: A pressure reducing valve (PRV)

Most plumbing codes mandate that if the static water pressure from the street main is in excess of 80 psi, a pressure reducing valve (PRV) must be installed to protect the pipes, fixtures, and appliances within the building from damage. The PRV is typically set to maintain a pressure between 50 and 60 psi.

Question 27: What is the function of a pressure regulator installed on a gas service?

To shut off gas flow automatically if pressure drops
To measure the volume of gas consumed
To filter sediment from the gas supply
To reduce and maintain steady downstream gas pressure (Correct answer)

Correct answer: To reduce and maintain steady downstream gas pressure

A pressure regulator reduces high-pressure gas from the supply main to the lower, steady pressure required by appliances.

Question 28: Which fixture requires a vented drain connection using a minimum 2-inch drain pipe per IPC?

Bathtub (Correct answer)
Lavatory
Floor drain
Kitchen sink

Correct answer: Bathtub

The IPC requires a minimum 1-1/2 inch drain for lavatories and kitchen sinks, but bathtubs require a minimum 1-1/2 inch drain; however, the drain fixture unit load typically requires 2 inches in many configurations — confirm with local amendments.

Question 29: According to most plumbing codes, what is the required range for a fixture trap's liquid seal depth?

3 inches to 5 inches
2 inches to 4 inches (Correct answer)
1 inch to 3 inches
4 inches to 6 inches

Correct answer: 2 inches to 4 inches

A trap seal between 2 and 4 inches is required to effectively block sewer gases while preventing siphonage or sluggish flow. A seal less than 2 inches is prone to evaporation or being siphoned out, and a seal deeper than 4 inches can slow drainage and lead to blockages.

Question 30: When multiple gas appliances share a common vent, the common vent must be sized to handle:

The average BTU input of connected appliances
The total combined BTU input of all connected appliances (Correct answer)
Only the largest appliance connected to it
The smallest appliance, with separate vents for others

Correct answer: The total combined BTU input of all connected appliances

A common vent must be sized for the total combined BTU input of all appliances that connect to it at any time.

Question 31: A gas appliance connector flexible hose may NOT be used to connect which type of appliance?

Water heater
Gas dryer
Gas range
Built-in oven (Correct answer)

Correct answer: Built-in oven

Built-in ovens are considered permanently installed appliances and must be connected with rigid piping, not flexible appliance connectors.

Question 32: An isometric drawing shows a horizontal drain with a 1/4" per foot slope over a 20-foot run. What is the total drop?

2.5 inches
20 inches
10 inches
5 inches (Correct answer)

Correct answer: 5 inches

Total drop = 1/4" × 20 = 5 inches over the 20-foot horizontal run.

Question 33: Which of the following is the most effective and code-approved method for protecting the potable water supply from contamination at a fixture by creating a physical separation?

Air Break
Air Gap (Correct answer)
Vacuum Breaker
Check Valve

Correct answer: Air Gap

An air gap is the unobstructed vertical space between the water supply outlet and the flood-level rim of a fixture. It is the most reliable and simplest form of backflow prevention because it creates a complete physical separation, preventing any contaminated water from siphoning back into the potable supply.

Question 34: Which installation configuration is acceptable for a pressure vacuum breaker (PVB)?

Installed at the same elevation as the highest downstream sprinkler head
Installed downstream of a shut-off valve that can be closed while PVB is under pressure
Installed upstream of any chemical injection points (Correct answer)
Installed in a pit or below grade where flooding can occur

Correct answer: Installed upstream of any chemical injection points

The PVB must always be installed upstream of any chemical injection or potential contamination source to provide protection.

Question 35: Cleanouts are required in a drainage system to allow for access. For a horizontal drainage pipe that is 100 feet long, where must cleanouts be located?

At the upper terminal and for each 50 feet of developed length.
Only at changes of direction greater than 90 degrees.
Only at the upper terminal end of the pipe.
At the upper terminal and for each 100 feet, or fraction thereof, of developed length. (Correct answer)

Correct answer: At the upper terminal and for each 100 feet, or fraction thereof, of developed length.

Plumbing codes require a cleanout at the upper terminal of each horizontal drain and for each 100 feet of developed length or fraction thereof. This ensures that the entire length of the pipe is accessible for cleaning and maintenance.

Question 36: A tankless (on-demand) water heater is rated primarily by:

BTU input and flow rate in gallons per minute (Correct answer)
Recovery rate in hours
Standby loss percentage
Storage capacity in gallons

Correct answer: BTU input and flow rate in gallons per minute

Tankless water heaters are rated by their BTU input and the flow rate (gpm) they can heat to a specified rise in temperature.

Question 37: The least amount of time that the system must be evaluated when evaluating gas piping installed in a single-family home with a volume of less than 10 cubic feet is _________________.

10 minutes (Correct answer)
15 minutes
60 minutes
30 minutes

Correct answer: 10 minutes

A test that is sustained for a minimum of 10 minutes is required for gas piping that is installed in a single-family residence and has a volume of less than 10 cubic feet. More than 24 hours cannot be spent maintaining testing. A manometer is the most widely used testing tool.

Question 38: When drawing a 3D pipe system in isometric view, pipes going into and out of the page (north-south) are drawn along which axis?

The vertical axis
The right-leaning 30-degree axis
The left-leaning 30-degree axis (Correct answer)
At true horizontal

Correct answer: The left-leaning 30-degree axis

The left-leaning 30-degree axis on an isometric drawing represents the north-south (depth) direction.

Question 39: An island fixture vent must loop to within how many inches of the underside of the counter?

6 inches (Correct answer)
3 inches
1 inch
12 inches

Correct answer: 6 inches

The island fixture vent must loop up to within 6 inches of the underside of the counter top before dropping back to connect to the drain.

Question 40: What is the purpose of a running trap installed on a building drain?

To allow air to enter the drain system
To separate stormwater from sewage
To reduce drain velocity
To prevent backflow of sewer gases into the building (Correct answer)

Correct answer: To prevent backflow of sewer gases into the building

A running trap (house trap) provides a water seal between the building drain and the public sewer to block sewer gases from entering the building.

Question 41: Which of the following can circuit vents do?

Tie into vent stacks
Tie into stack vents
All of the above (Correct answer)
Tie into another vent that extends to outside air

Correct answer: All of the above

Ventilating a battery of fixtures requires the use of circuit vents. The vents might be connected to other vents that open to the outdoors. Vent stacks and stack vents are included in this. A circuit vent must have a diameter that is at least half that of the drain it is intended to serve.

Question 42: When sizing a building drain, the total fixture unit load must be compared to which variable?

The building height
The water supply pressure
The pipe diameter and slope (Correct answer)
The pipe material only

Correct answer: The pipe diameter and slope

Building drain sizing tables in the IPC use both the pipe diameter and the installed slope to determine the maximum allowable drainage fixture unit load.

Question 43: Which document primarily governs plumbing installations in most US jurisdictions?

ANSI A112.18
International Plumbing Code (IPC) or Uniform Plumbing Code (UPC) (Correct answer)
NFPA 13
OSHA 29 CFR 1910

Correct answer: International Plumbing Code (IPC) or Uniform Plumbing Code (UPC)

Most US jurisdictions adopt either the IPC or UPC as their primary plumbing code.

Question 44: In pipe measurement, the dimension that must be subtracted from a center-to-center measurement to determine the exact cut length of the pipe is known as:

Fitting allowance (Correct answer)
Throw
Developed length
Travel

Correct answer: Fitting allowance

The fitting allowance, or take-off, is the length from the center of a fitting to the face of the fitting's socket or hub. This amount is subtracted from the center-to-center measurement for each fitting used to find the precise cut length of the pipe.

Question 45: It is necessary to pipe clear water waste from a potable source through an air gap, such as a relief valve on a water heater, to an indirect waste.

TRUE (Correct answer)
FALSE

Correct answer: TRUE

It is required to pipe clear water waste from a potable water system to an indirect waste and discharge it through an air gap. This is as easy as terminating the discharge pipe of a floor drain six inches above the strainer.

Question 46: Which pipe material is NOT approved for use with natural gas in residential installations under NFPA 54?

CSST (corrugated stainless steel tubing)
Copper tubing (Type K or L)
PVC plastic pipe (Correct answer)
Black steel pipe

Correct answer: PVC plastic pipe

PVC plastic pipe is not permitted for gas piping because it cannot withstand the temperatures and pressures involved and is not listed for gas service.

Question 47: A journeyman plumber is installing fixtures in an ADA-compliant public restroom. What is the required height range for the toilet seat above the finished floor?

20 to 22 inches
23 to 25 inches
17 to 19 inches (Correct answer)
14 to 16 inches

Correct answer: 17 to 19 inches

The Americans with Disabilities Act (ADA) standards require that the top of the toilet seat in an accessible restroom be between 17 and 19 inches above the finished floor. This height makes it easier for individuals with mobility impairments, particularly those transferring from a wheelchair, to use the fixture.

Question 48: Under IPC, what is required when a plumbing vent pipe passes through a roof?

It must be capped with a mesh screen to prevent insect entry
It must be increased one pipe size above the roof line
It must be connected to a stack vent within 12 inches of the roof
It must extend at least 6 inches above the roof surface (Correct answer)

Correct answer: It must extend at least 6 inches above the roof surface

The IPC requires vent pipes to extend at least 6 inches above the roof to prevent blockage by snow or debris.

Question 49: What is the minimum BTU/hr input for a gas-fired water heater to require a dedicated combustion air opening?

The requirement is based on the room volume, not the BTU rating alone (Correct answer)
50,000 BTU/hr
100,000 BTU/hr
75,000 BTU/hr

Correct answer: The requirement is based on the room volume, not the BTU rating alone

Combustion air requirements are determined by the total BTU input of all appliances in the space relative to the available room volume, not a single BTU threshold.

Question 50: A plumber is installing a new natural gas piping system that will operate at a standard pressure of 7 inches water column (approx. 0.25 psi). According to the International Fuel Gas Code (IFGC), what is the minimum required air pressure test for this new installation?

0.5 psig for a minimum of 30 minutes
10 psig for a minimum of 5 minutes
3 psig for a minimum of 10 minutes (Correct answer)
1.5 times the operating pressure for 15 minutes

Correct answer: 3 psig for a minimum of 10 minutes

According to IFGC section 406.4.1, for a gas system with a proposed maximum working pressure less than or equal to 0.5 psi, the test pressure must be no less than 1.5 times the working pressure, but not less than 3 psig. The test duration must be a minimum of 10 minutes.

Question 51: The minimum slope for a 3-inch horizontal drain pipe under IPC is:

1/4 inch per foot (Correct answer)
1/2 inch per foot
1/8 inch per foot
1 inch per foot

Correct answer: 1/4 inch per foot

A 3-inch drain pipe requires a minimum slope of 1/4 inch per foot to ensure proper self-scouring flow.

Question 52: Which of the following best describes back-pressure (positive pressure) in a drainage stack?

Negative pressure caused by a fast-moving slug of water in the stack
Pressure loss from undersized vent pipes
Water pressure from the supply system entering the drain
Pressure that builds below a slug of falling water and can push trap seals into the room (Correct answer)

Correct answer: Pressure that builds below a slug of falling water and can push trap seals into the room

As a slug of water falls down a tall stack, it compresses air below it, creating positive pressure that can force trap seals out of lower-floor fixture traps.

Question 53: What substance is added to natural gas to give it its distinctive odor?

Mercaptan (ethyl mercaptan) (Correct answer)
Propane
Carbon monoxide
Methane

Correct answer: Mercaptan (ethyl mercaptan)

Mercaptan (ethyl mercaptan) is the odorant added to natural gas by the utility to make odorless gas detectable by smell at very low concentrations.

Question 54: What is the maximum length of an unprotected flexible appliance connector used on a gas range?

6 feet (Correct answer)
3 feet
12 feet
2 feet

Correct answer: 6 feet

Flexible connectors must not exceed 6 feet and must be the listed connector type appropriate for the appliance.

Question 55: A circuit vent is connected to a horizontal branch drain at what location relative to the fixture connections?

Upstream of the first fixture
Downstream of the last fixture (Correct answer)
At the stack connection
Between the first and last fixtures

Correct answer: Downstream of the last fixture

A circuit vent connects to the horizontal branch drain downstream (below) the last fixture connection on that branch.

Question 56: Which of the following best describes a 'critical level' (CL) marking on a backflow prevention device?

The flood level of the fixture it protects
The minimum flow rate required for the device to operate
The level below which the device must not be installed to prevent backsiphonage (Correct answer)
The maximum water pressure rating of the device

Correct answer: The level below which the device must not be installed to prevent backsiphonage

The CL mark indicates the lowest point of installation to ensure the device functions correctly and prevents back-siphonage.

Question 57: A combination waste and vent system is typically permitted for which type of fixture?

Lavatories and bidets only
Bathtubs and showers only
Floor drains and floor sinks (Correct answer)
Water closets and urinals

Correct answer: Floor drains and floor sinks

Combination waste and vent systems are commonly permitted for floor drains and floor sinks in commercial settings where wet venting is impractical.

Question 58: What test is commonly used to check a completed DWV system for leaks before covering it?

Hydrostatic pressure test at 100 psi
Air pressure test at 5 psi or water test filled to the highest point (Correct answer)
Dye test using colored water from the supply system
Vacuum test at 15 inches Hg

Correct answer: Air pressure test at 5 psi or water test filled to the highest point

DWV systems are tested with either an air test at 5 psi or a water test where the system is filled to the level of the highest stack opening, per IPC Section 312.

Question 59: Which document primarily governs gas piping installation standards for most US jurisdictions?

IPC (International Plumbing Code)
NEC (National Electrical Code)
ASME B31.1 Power Piping
NFPA 54 / International Fuel Gas Code (IFGC) (Correct answer)

Correct answer: NFPA 54 / International Fuel Gas Code (IFGC)

NFPA 54 (National Fuel Gas Code) and its companion IFGC are the primary standards adopted by most US jurisdictions for fuel gas piping installation.

Question 60: What is the maximum vertical distance a fixture drain may drop before connecting to the trap arm?

The drain must connect directly to the trap with no vertical drop
There is no vertical limit
One pipe diameter
The trap arm must be level or pitched to drain only (Correct answer)

Correct answer: The trap arm must be level or pitched to drain only

The trap arm must be level or pitched toward the drain at no more than 1/4 inch per foot — no section between the trap and vent may be vertical.

Question 61: What is the minimum clearance required between a gas appliance vent connector and combustible materials?

3 inches
9 inches
6 inches (Correct answer)
1 inch

Correct answer: 6 inches

NFPA 54 requires a minimum 6-inch clearance between single-wall metal vent connectors and combustible materials.

Question 62: When performing a water test on a newly installed DWV (Drain, Waste, and Vent) system, what is the minimum required head of water that must be applied to the system and for what duration, according to the IPC?

A head equal to a 2-story building (approx. 20 feet) for 30 minutes.
The system must be filled to the point of overflow for 5 minutes.
5 feet of head for 10 minutes.
10 feet of head for 15 minutes. (Correct answer)

Correct answer: 10 feet of head for 15 minutes.

According to IPC Section 312.2, a water test on a DWV system requires it to be subjected to not less than a 10-foot head of water. This pressure must be held for a minimum of 15 minutes without any evidence of leakage.

Question 63: An air admittance valve (AAV) may NOT be used as the sole means of venting in which location?

As the vent for a building sewer (Correct answer)
On the branch drain of a bathroom group
In an attic space above insulation
Under a kitchen sink cabinet

Correct answer: As the vent for a building sewer

AAVs cannot be used to vent a building sewer because they are one-way devices and do not allow sewer gases to escape to atmosphere.

Question 64: A plumber is analyzing an isometric drawing for a drain line that requires a 45-degree offset. The drawing shows the offset distance (the center-to-center distance between the parallel pipes) is 24 inches. What is the required travel, or true length, of the pipe between the two 45-degree fittings?

24.0 inches
48.0 inches
28.8 inches
33.9 inches (Correct answer)

Correct answer: 33.9 inches

The formula to calculate the travel piece for a 45-degree offset is: Travel = Offset × 1.414. In this scenario, 24 inches × 1.414 = 33.936 inches, which is rounded to 33.9 inches. This constant is derived from the properties of a 45-45-90 triangle.

Question 65: A manual shutoff valve must be installed within what distance of each gas appliance?

5 feet
10 feet
6 feet (Correct answer)
3 feet

Correct answer: 6 feet

The IFGC requires a manual shutoff valve to be installed within 6 feet of each gas appliance to allow for quick isolation in an emergency.

Question 66: Which backflow device is NOT acceptable for use under continuous supply pressure?

Double check valve assembly (DCVA)
Pressure vacuum breaker (PVB)
Reduced pressure zone (RPZ)
Atmospheric vacuum breaker (AVB) (Correct answer)

Correct answer: Atmospheric vacuum breaker (AVB)

Atmospheric vacuum breakers must not be subjected to continuous supply pressure exceeding 12 hours as it can hold the check open, defeating the device.

Question 67: A plumber is installing a water closet in a residential bathroom. According to most model plumbing codes, what is the minimum required clearance from the centerline of the water closet to any side wall or partition?

18 inches
21 inches
12 inches
15 inches (Correct answer)

Correct answer: 15 inches

Most plumbing codes, including the International Plumbing Code (IPC) and Uniform Plumbing Code (UPC), mandate a minimum of 15 inches from the centerline of a water closet to any adjacent wall, partition, or vanity. This ensures adequate space for use and cleaning.

Question 68: Under IPC, what is the maximum developed length of a trap arm (from trap weir to vent) for a 1-1/2 inch pipe?

3 feet
8 feet
6 feet
5 feet (Correct answer)

Correct answer: 5 feet

The IPC allows a maximum trap arm length of 5 feet for a 1-1/2 inch pipe.

Question 69: A thermostatic mixing valve on a water heater is set to supply domestic hot water at:

100°F to 105°F
130°F to 140°F
110°F to 115°F (Correct answer)
120°F to 125°F

Correct answer: 110°F to 115°F

Thermostatic mixing valves are typically set to deliver domestic hot water at 110°F–115°F, balancing scald prevention with Legionella control.

Question 70: Which of the following conditions ALWAYS requires a licensed plumber or gas fitter to obtain a permit before work begins?

Installing new gas piping or extending an existing gas line (Correct answer)
Lighting a pilot light
Replacing an existing gas appliance connector (same size)
Cleaning a burner orifice

Correct answer: Installing new gas piping or extending an existing gas line

Any new gas piping installation or extension of an existing gas system requires a permit to ensure the work is inspected and meets code.

Question 71: Which fitting is required when connecting CSST (corrugated stainless steel tubing) to a rigid gas appliance connector?

A manufacturer-approved mechanical fitting (Correct answer)
A flare fitting
A compression fitting
A sweated solder fitting

Correct answer: A manufacturer-approved mechanical fitting

CSST must be connected using manufacturer-approved mechanical fittings specifically designed for the product, as improper fittings can cause leaks or damage.

Question 72: A floor drain trap primer is used to:

Prime the sewer ejector pump before use
Clean the floor drain screen automatically
Periodically supply water to a floor drain trap to prevent the seal from evaporating (Correct answer)
Increase the flow rate through the floor drain

Correct answer: Periodically supply water to a floor drain trap to prevent the seal from evaporating

Trap primers supply small amounts of water to infrequently used floor drain traps to replace water lost to evaporation and maintain the sewer gas seal.

Question 73: Which device provides the highest level of backflow protection and is required for high-hazard connections?

Reduced pressure zone (RPZ) assembly (Correct answer)
Pressure vacuum breaker
Double check valve assembly
Atmospheric vacuum breaker

Correct answer: Reduced pressure zone (RPZ) assembly

The reduced pressure zone assembly is the highest-rated mechanical backflow preventer and is required for high-hazard cross-connections such as chemical feed lines.

Question 74: An isometric drawing shows a rolling offset where a vent pipe rises 15 inches vertically and offsets 20 inches horizontally, using 45-degree fittings. What is the center-to-center length of the travel pipe required for this offset?

49.49 inches
35.35 inches (Correct answer)
25.00 inches
28.28 inches

Correct answer: 35.35 inches

This requires a two-step calculation. First, find the 'true offset' using the Pythagorean theorem (a² + b² = c²), where 'a' is the rise and 'b' is the horizontal offset. True Offset = √(15² + 20²) = √(225 + 400) = √625 = 25 inches. Second, calculate the travel piece by multiplying the true offset by the 45-degree constant: 25" × 1.414 = 35.35 inches.

Question 75: A sanitary tee may be used in a drainage system in which orientation?

On its back in a horizontal run
Horizontally with the branch pointing up
In a vertical stack receiving horizontal branch connections (Correct answer)
As a horizontal-to-horizontal fitting only

Correct answer: In a vertical stack receiving horizontal branch connections

Sanitary tees are approved for use in the vertical position where a horizontal branch connects to a vertical stack.

Question 76: A plumber is installing 1-inch Schedule 40 steel pipe for a horizontal natural gas run. According to common piping standards (ASME B31.1), what is the maximum recommended support spacing for this horizontal pipe?

4 feet
12 feet
6 feet
8 feet (Correct answer)

Correct answer: 8 feet

While specific local codes may vary, standard engineering practices such as those referenced in ASME B31.1 provide tables for maximum support spacing. For 1-inch nominal steel pipe, the suggested maximum span is typically around 8 feet for gas service to prevent sagging and stress on the joints. Some tables might show 9 feet, but 8 feet is a very common and safe standard.

Question 77: When installing a propane (LP) system, the tank must be located a minimum of how far from any building opening?

3 feet
10 feet (Correct answer)
25 feet
5 feet

Correct answer: 10 feet

NFPA 58 requires LP-gas containers to be located at least 10 feet from any building opening such as windows, doors, or dryer vents.

Question 78: Which situation requires a backflow preventer on a potable water supply to a boiler?

When chemical treatment is added to the boiler water (Correct answer)
When the boiler is gas-fired
When the boiler is on the same floor as the meter
When the boiler operates below 212°F

Correct answer: When chemical treatment is added to the boiler water

Chemical additives in boiler water create a high-hazard cross-connection, requiring at minimum an RPZ assembly to protect the potable supply.

Question 79: A natural gas vent for a Category I appliance terminates through a pitched roof. What is the minimum height the vent must extend above the point where it passes through the roof surface?

6 inches
24 inches
12 inches (Correct answer)
18 inches

Correct answer: 12 inches

According to typical fuel gas codes, a vent must terminate at least a certain height above the roof to ensure proper draft and prevent blockage from snow or debris. For vents passing through a roof, a common minimum height requirement is 12 inches (1 foot), though this can increase depending on the roof pitch and proximity to vertical surfaces. For example, some codes require termination at least 2 feet higher than any portion of the building within 10 feet.

Question 80: An isometric drawing shows a 60° offset on a 3-inch pipe. If the set (offset distance) is 9 inches, what is the approximate travel?

10.4 inches (Correct answer)
18 inches
7.8 inches
12.7 inches

Correct answer: 10.4 inches

For a 60° offset, travel = set ÷ sin(60°) = 9 ÷ 0.866 ≈ 10.4 inches.

Question 81: A plumber finds that an existing 4-inch cast iron drain is cracked and must be replaced with PVC. The transition coupling used between cast iron and PVC must be:

A threaded iron-to-PVC adapter
A listed mechanical (Fernco-type) transition coupling (Correct answer)
A lead and oakum joint
A standard PVC slip coupler

Correct answer: A listed mechanical (Fernco-type) transition coupling

A listed mechanical transition (shielded) coupling is required to join dissimilar pipe materials like cast iron and PVC.

Journeyman Plumber Exam

The Journeyman Plumber Exam exam validates essential knowledge and skills required for certification or licensure in this field.

Questions

120 min

Time Limit

70%

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