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Question 1Plumbing Code, Rules, and Licensing Requirements

A homeowner in Oklahoma wants to pay a neighbor to replace a water heater and repipe a bathroom. Under state licensing rules, who is permitted to perform this work for compensation?

  1. An apprentice plumber who works without on-site supervision
  2. A handyman who holds a general contractor license
  3. A licensed journeyman or master plumber Correct answer.
  4. Any person the homeowner names in a written agreement

Explanation

Oklahoma law limits plumbing work performed for compensation to persons who hold a plumbing license and work under a licensed plumbing contractor. Apprentices may work only while supervised by a licensed plumber, and a general contractor license does not authorize plumbing. A private agreement with the homeowner does not create legal authority to do the work.

Question 2Plumbing Code, Rules, and Licensing Requirements

An apprentice plumber is assigned to rough-in a bathroom group. Under state rules, the apprentice's work must be performed:

  1. Only with plastic pipe and fittings
  2. Inspected by the building official before the apprentice begins
  3. With a written log filed with the state each week
  4. Under the supervision of a licensed plumber Correct answer.

Explanation

Apprentices may perform plumbing work only while under the direction and supervision of a licensed plumber, who remains responsible for the installation. The rules do not restrict apprentices to a single piping material, and no weekly filing of work logs with the state is required.

Question 3Plumbing Code, Rules, and Licensing Requirements

Each fixture trap shall have a liquid seal of not less than 2 inches and not more than:

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

Explanation

The trap seal must be deep enough to resist pressure fluctuations but shallow enough to be cleared by the fixture's flow. The code sets the seal at a minimum of 2 inches and a maximum of 4 inches, measured from the trap weir to the top of the dip.

Question 4Plumbing Code, Rules, and Licensing Requirements

A 3-inch horizontal drainage pipe serving a group of fixtures must be installed at a slope of not less than:

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

Explanation

Horizontal drainage pipe must slope toward the point of disposal at a rate that keeps solids moving. Pipe 2-1/2 inches and smaller requires 1/4 inch per foot, pipe 3 through 6 inches requires 1/8 inch per foot, and 8-inch and larger pipe requires 1/16 inch per foot.

Question 5Plumbing Code, Rules, and Licensing Requirements

The discharge pipe from a water heater temperature and pressure relief valve shall terminate:

  1. Directly into the water heater drain pan
  2. At least 12 inches above the floor drain
  3. Within 6 inches of the floor, unthreaded Correct answer.
  4. Outside the building at least 7 feet above grade

Explanation

The relief valve discharge pipe must run full size, slope downward, and terminate by gravity flow not more than 6 inches above the floor or a waste receptor. The end must be unthreaded and must not be trapped so that the discharge is never restricted or capped.

Question 6Plumbing Code, Rules, and Licensing Requirements

A residential dishwasher's drain line must be connected to the drainage system by:

  1. A direct connection to the sink tailpiece with a hose clamp
  2. A connection to the sink trap arm upstream of the vent
  3. A trap with a 2-inch seal dedicated to the appliance
  4. An indirect connection through an air gap or air break Correct answer.

Explanation

The dishwashing machine drain must connect indirectly through an air gap or air break so that sewage or suds cannot siphon back into the appliance. The indirect connection discharges to a fixture drain or waste receptor that is properly trapped and vented.

Question 7Plumbing Code, Rules, and Licensing Requirements

A vent stack extending through a roof used only for weather protection shall extend not less than:

  1. 18 inches above the roof surface
  2. 3 feet above the roof surface
  3. 6 inches above the roof surface Correct answer.
  4. 12 inches above the roof surface

Explanation

A vent must terminate outdoors above the roof so that gases are released away from the building. The minimum extension is 6 inches above the roof surface; where the roof is used for purposes other than weather protection, the vent must extend at least 7 feet above the roof.

Question 8Plumbing Code, Rules, and Licensing Requirements

For a fixture such as a flush-tank water closet or a lavatory, the minimum required flow pressure at the fixture is:

  1. 20 psi
  2. 3 psi
  3. 15 psi
  4. 8 psi Correct answer.

Explanation

Most fixtures supplied through a flush tank or supplied at a faucet require a flow pressure of at least 8 psi at the outlet. Higher pressures, such as 20 to 25 psi, apply to flushometer valves and other special fixtures.

Question 9Plumbing Code, Rules, and Licensing Requirements

On a horizontal building drain of 4-inch pipe, cleanouts shall be installed at intervals not exceeding:

  1. 200 feet
  2. 75 feet
  3. 100 feet Correct answer.
  4. 50 feet

Explanation

Cleanouts must be spaced closely enough that the entire drain can be rodded from a cleanout. For pipe 4 inches and smaller the interval may not exceed 100 feet; for pipe larger than 4 inches the maximum interval is 200 feet.

Question 10Plumbing Code, Rules, and Licensing Requirements

The smallest fixture drain that may serve a water closet is:

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

Explanation

A water closet discharges a large volume of water and solids in a short period, so its fixture drain must be at least 3 inches in diameter. Smaller drains such as 2 inches are suitable for lavatories and similar fixtures but not for water closets.

Question 11Plumbing Code, Rules, and Licensing Requirements

When a potable water outlet discharges into a receiving fixture through an air gap, the gap must be at least:

  1. One-half the pipe diameter
  2. One-half inch
  3. Twice the pipe diameter Correct answer.
  4. Four times the pipe diameter

Explanation

An air gap is the unobstructed vertical distance between the supply outlet and the flood level rim of the receiving fixture. It must be at least twice the effective opening of the outlet and in no case less than 1 inch.

Question 12Plumbing Code, Rules, and Licensing Requirements

A water heater drain pan shall be not less than 1-1/2 inches deep and shall be drained by a pipe not less than:

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

Explanation

A drain pan under a water heater must be at least 1-1/2 inches deep and drain through a pipe at least 3/4 inch in size. The pan drain must discharge to an approved indirect waste receptor.

Question 13Plumbing Code, Rules, and Licensing Requirements

A floor drain in a building drains to a point below the level of the next upstream manhole. The fixture branch must be protected by:

  1. An air admittance valve on the trap arm
  2. A vent check valve in the fixture vent
  3. A trap primer at the floor drain
  4. A backwater valve on the fixture branch Correct answer.

Explanation

Fixtures that drain below the level of the next upstream manhole are subject to sewage backing up into the building. Such fixtures must drain through an approved backwater valve, or be provided with another approved means of preventing backflow.

Question 14Plumbing Code, Rules, and Licensing Requirements

The maximum flow rate for a single showerhead, measured at 80 psi, is:

  1. 2.5 gpm Correct answer.
  2. 1.5 gpm
  3. 1.0 gpm
  4. 3.5 gpm

Explanation

Federal energy standards adopted through the plumbing code limit a single showerhead to 2.5 gallons per minute at 80 psi flowing pressure. This limit applies to the total flow of a shower assembly unless it uses multiple separately controlled heads.

Question 15Plumbing Code, Rules, and Licensing Requirements

A water closet is centered in a 30-inch-wide alcove with finished sidewalls. The installation is:

  1. Not permitted; each side clearance must be 18 inches
  2. Permitted, because each side clearance is 15 inches Correct answer.
  3. Permitted only if the compartment is 5 feet deep
  4. Not permitted; the alcove must be at least 36 inches wide

Explanation

A water closet must have at least 15 inches of clear space from its centerline to any sidewall or partition. Centering the fixture in a 30-inch alcove yields exactly 15 inches on each side, which satisfies the clearance, and 21 inches of clearance must also be provided in front.

Question 16Plumbing Code, Rules, and Licensing Requirements

Cleanouts serving drainage pipe 4 inches and smaller shall be:

  1. The same nominal size as the pipe Correct answer.
  2. Not less than 2 inches larger than the pipe
  3. A minimum of 6 inches in diameter
  4. One nominal size smaller than the pipe

Explanation

A cleanout must be large enough to pass the debris and the rodding tool for the pipe it serves. Cleanouts on pipe up to 4 inches are the same nominal size as the pipe; for larger pipe the cleanout is not less than 4 inches.

Question 17Plumbing Code, Rules, and Licensing Requirements

Solder and flux used to join potable water piping must be lead free, which means a weighted average lead content of not more than:

  1. 0.25 percent Correct answer.
  2. 8 percent
  3. 2 percent
  4. 0.02 percent

Explanation

Materials in contact with potable water must be lead free to limit lead exposure at the tap. The standard defines lead free as a weighted average lead content of not more than 0.25 percent in the wetted surface area.

Question 18Plumbing Code, Rules, and Licensing Requirements

A backflow preventer is installed on the water service to a building. The potable water system must also be provided with:

  1. An additional water meter bypass
  2. A vacuum relief valve on the water heater
  3. A pressure-reducing valve set at 50 psi
  4. A means to control thermal expansion Correct answer.

Explanation

A backflow preventer or check valve closes the system to the public main, making the building system a closed system. Warmed water then has no place to expand, so the code requires a device or method to control thermal expansion.

Question 19Plumbing Code, Rules, and Licensing Requirements

A floor drain is installed in a location where the trap seal may be lost by evaporation. The drain must be provided with:

  1. A backwater valve
  2. A trap seal primer Correct answer.
  3. An air admittance valve
  4. A larger trap

Explanation

When a trap seal is subject to evaporation, such as a floor drain in an unused area, sewer gas can enter the building through the dry trap. The code requires an approved trap seal primer, or another approved method, to keep the seal maintained.

Question 20Plumbing Code, Rules, and Licensing Requirements

A 2-inch trap arm installed at the required slope may have a developed length from the trap weir to the vent of not more than:

  1. 16 feet
  2. 8 feet Correct answer.
  3. 5 feet
  4. 12 feet

Explanation

The distance from the trap weir to the vent is limited so that the trap is not self-siphoned when the fixture drains. For a 2-inch trap arm at 1/4 inch per foot, the maximum developed length is 8 feet; longer distances require a larger trap arm.

Question 21Plumbing Code, Rules, and Licensing Requirements

A 4-inch building drain has a straight horizontal run of 250 feet, with cleanouts installed at both ends. How many additional cleanouts are required?

  1. Two Correct answer.
  2. No additional cleanouts are required
  3. Three
  4. One

Explanation

Cleanouts on 4-inch horizontal drainage pipe may not be more than 100 feet apart. With cleanouts at each end of the 250-foot run, additional cleanouts at roughly 100 feet and 200 feet keep every interval at or under the limit.

Question 22Plumbing Code, Rules, and Licensing Requirements

A 4-inch horizontal drainage branch 60 feet long is installed at the minimum slope for that pipe size. The total fall over the run is:

  1. 2-1/2 inches
  2. 7-1/2 inches Correct answer.
  3. 5 inches
  4. 15 inches

Explanation

Four-inch drainage pipe may be installed at 1/8 inch per foot, so the fall equals 60 feet multiplied by 1/8 inch per foot. That gives 7-1/2 inches of total fall over the run.

Question 23Plumbing Code, Rules, and Licensing Requirements

Where a DWV system is tested with air, the required test pressure and duration are:

  1. 50 psi for 60 minutes
  2. 10 psi for 30 minutes
  3. 5 psi for 15 minutes Correct answer.
  4. 15 psi for 10 minutes

Explanation

An air test on a drainage, waste, and vent system is made with a gauge pressure of not less than 5 psi held for 15 minutes with no drop in pressure. A water test, by contrast, uses a 10-foot head of water above the highest connection.

Question 24Plumbing Code, Rules, and Licensing Requirements

The minimum diameter of an individual vent serving a plumbing fixture is:

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

Explanation

An individual fixture vent must be at least 1-1/4 inches in diameter, though it may have to be increased where the fixture drain is larger or the vent length requires it. Half-inch and three-quarter-inch pipe are not permitted as vents.

Question 25Plumbing Code, Rules, and Licensing Requirements

A cleanout shall be installed at the base of each:

  1. Water heater relief line
  2. Vertical vent
  3. Fixture supply branch
  4. Waste or soil stack Correct answer.

Explanation

A cleanout is required where a waste or soil stack turns horizontal at its base, because that is where blockages most often occur and where rodding access is needed. Vents, relief valve discharge lines, and supply branches do not require cleanouts.

Question 26Plumbing Code, Rules, and Licensing Requirements

The maximum water consumption for a tank-type water closet is:

  1. 3.5 gallons per flush
  2. 2.5 gallons per flush
  3. 1.6 gallons per flush Correct answer.
  4. 1.28 gallons per flush

Explanation

Water closets are limited to a maximum flush volume of 1.6 gallons, a standard that has applied to tank-type closets for many years. Lower volumes such as 1.28 gallons are permitted but not required.

Question 27Plumbing Code, Rules, and Licensing Requirements

The liquid depth of a fixture trap seal shall be:

  1. not less than 2 inches and not more than 3 inches
  2. not less than 1 inch and not more than 2 inches
  3. not less than 3 inches and not more than 5 inches
  4. not less than 2 inches and not more than 4 inches Correct answer.

Explanation

A trap seal must be deep enough to resist evaporation and pressure fluctuations, but shallow enough that a blockage or pressure surge can break it. The code window is 2 inches minimum and 4 inches maximum of liquid seal.

Question 28Plumbing Code, Rules, and Licensing Requirements

Before a new drainage and vent system is concealed behind finished walls, the plumber must:

  1. wait one full working day after the rough-in is complete
  2. submit as-built drawings to the state health department
  3. notify the local water utility that the rough-in is finished
  4. request an inspection and obtain approval of the work Correct answer.

Explanation

Work that will be covered must be inspected and approved while it is still exposed, so the code official can verify sizing, slope, joints, and support. Concealing piping before approval is a common violation.

Question 29Plumbing Code, Rules, and Licensing Requirements

The minimum slope for a 3-inch horizontal drainage pipe is:

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

Explanation

Drainage slope is based on pipe size: 2-1/2 inch and smaller pipe must slope at 1/4 inch per foot, while 3-inch through 6-inch pipe may slope at 1/8 inch per foot. Larger pipe may use still flatter grades.

Question 30Plumbing Code, Rules, and Licensing Requirements

The vertical distance from a fixture outlet to the trap weir shall not exceed:

  1. 18 inches
  2. 12 inches
  3. 24 inches Correct answer.
  4. 36 inches

Explanation

Keeping the trap close to the fixture outlet prevents a long vertical tailpiece from creating excessive velocity and self-siphonage of the seal. The limit from the fixture outlet down to the trap weir is 24 inches.

Question 31Plumbing Code, Rules, and Licensing Requirements

The maximum flow rate for a lavatory faucet, measured at 60 psi, is:

  1. 2.2 gallons per minute Correct answer.
  2. 3.0 gallons per minute
  3. 1.5 gallons per minute
  4. 2.5 gallons per minute

Explanation

Lavatory faucets are limited to 2.2 gallons per minute when tested at 60 psi. The same 2.2 gpm ceiling applies to kitchen sink faucets.

Question 32Plumbing Code, Rules, and Licensing Requirements

In Oklahoma, plumbing licenses are issued and regulated by the:

  1. Oklahoma State Department of Health
  2. Oklahoma Water Resources Board
  3. Oklahoma Department of Environmental Quality
  4. Construction Industries Board Correct answer.

Explanation

Plumbing licensure in Oklahoma is administered by the Construction Industries Board, which issues journeyman, master, and contractor licenses and enforces the licensing law. Plumbing work for pay must be performed under a license issued by that board.

Question 33Plumbing Code, Rules, and Licensing Requirements

The minimum size of a fixture drain for a lavatory is:

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

Explanation

The code minimum fixture drain size for a lavatory is 1-1/4 inches, which matches the usual 1-1/4 inch trap and tailpiece. Larger pipe is permitted but not required.

Question 34Plumbing Code, Rules, and Licensing Requirements

The water distribution system of a building shall be tested, in a completed state, at a pressure of at least:

  1. 125 psi for 45 minutes
  2. 75 psi for 30 minutes
  3. 150 psi for 2 hours
  4. 100 psi for 60 minutes Correct answer.

Explanation

Potable water piping is tested at a pressure not less than the working pressure, and the code minimum test is 100 psi held for 60 minutes with no drop. The test verifies that joints and fittings are leak free before the system is concealed.

Question 35Plumbing Code, Rules, and Licensing Requirements

Horizontal PVC drainage piping shall be supported at intervals not exceeding:

  1. 10 feet
  2. 4 feet Correct answer.
  3. 12 feet
  4. 6 feet

Explanation

Plastic DWV pipe sags more readily than metal pipe, so the code sets a shorter support interval of 4 feet for horizontal runs. Vertical plastic stacks are supported at each story or at the intervals listed for the material.

Question 36Plumbing Code, Rules, and Licensing Requirements

A tank-type water closet rated at 1.6 gallons per flush has a drainage fixture unit value of:

  1. 3 fixture units Correct answer.
  2. 1 fixture unit
  3. 2 fixture units
  4. 4 fixture units

Explanation

In the drainage fixture unit table, a water closet with a 1.6 gallon flush is assigned 3 fixture units. This value is used when adding loads to size branches, stacks, and the building drain.

Question 37Plumbing Code, Rules, and Licensing Requirements

A temperature and pressure relief valve on a storage water heater shall be rated to open at a maximum of:

  1. 225 degrees F and 175 psi
  2. 250 degrees F and 200 psi
  3. 180 degrees F and 100 psi
  4. 210 degrees F and 150 psi Correct answer.

Explanation

Relief valves for storage water heaters must be rated not to exceed 210 degrees F and 150 psi, which corresponds to the standard listing for this device. The valve's rating also may not exceed the working pressure of the tank.

Question 38Plumbing Code, Rules, and Licensing Requirements

The entire length of a horizontal vent shall be installed not less than:

  1. 6 inches above the flood level rim of the highest fixture served Correct answer.
  2. 6 inches above the trap weir of the highest fixture served
  3. 12 inches above the flood level rim of the fixture served
  4. 12 inches above the floor level of the highest fixture served

Explanation

A horizontal vent must stay above the flood level rim of the highest fixture it serves so that a backed-up fixture cannot flood the vent with waste. The required clearance is 6 inches above that rim for the entire length of the horizontal vent.

Question 39Plumbing Code, Rules, and Licensing Requirements

The building drain extends from the lowest piping inside the building to a point:

  1. 30 inches outside the building wall Correct answer.
  2. at the property line
  3. at the inside face of the foundation wall
  4. 60 inches outside the building wall

Explanation

By definition, the building drain carries the building's discharge to a point 30 inches outside the building wall, where the building sewer begins. The building sewer then continues from that point to the public sewer or private disposal system.

Question 40Plumbing Code, Rules, and Licensing Requirements

A 50-gallon tank-type water heater is installed in a second-floor closet directly above a finished ceiling. Where leakage from the heater or its connections could cause damage, the required drain pan must:

  1. be at least 1-1/2 inches deep with a 3/4-inch drain piped to a conspicuous point of disposal Correct answer.
  2. be provided only when the heater is fuel-gas fired and installed above the first floor
  3. be at least 4 inches deep with a 1-inch drain connected directly to the building drain
  4. be at least 1-1/2 inches deep with a 1/2-inch drain discharging into a floor drain receptor

Explanation

Where a water heater is installed in a location where leakage may cause damage, the code requires a watertight pan under the appliance. The pan must be at least 1-1/2 inches deep and must have a drain of not less than 3/4-inch nominal pipe size that terminates at a conspicuous point of disposal. The drain may not be directly connected to the drainage system, and the requirement applies regardless of the heater's energy source.

Question 41Water Supply and Distribution

What is the unobstructed vertical distance between the lowest opening of a water supply outlet and the flood-level rim of the fixture it serves called?

  1. An air chamber
  2. An air gap Correct answer.
  3. A backflow preventer
  4. A vacuum breaker

Explanation

An air gap is the physical separation between a supply outlet and the flood-level rim of the receiving fixture. Because there is no continuous connection, contaminated water cannot travel back into the potable supply, making it the most reliable form of backflow protection.

Question 42Water Supply and Distribution

A building receives water from the street main at about 115 psi. Which device is required to bring the pressure down to a safe level for the building distribution system?

  1. A gate valve
  2. A pressure-reducing valve Correct answer.
  3. A spring-loaded check valve
  4. A pressure-relief valve

Explanation

The plumbing code requires a pressure-reducing valve where static pressure in the distribution system exceeds 80 psi. A reducing valve automatically throttles the incoming flow to hold a lower, adjustable downstream pressure, commonly in the 50 to 60 psi range.

Question 43Water Supply and Distribution

What is the function of a water hammer arrestor installed near a quick-closing valve?

  1. To raise the working pressure in the branch
  2. To purge entrained air from the piping
  3. To measure the volume of water used
  4. To absorb shock from sudden pressure changes Correct answer.

Explanation

Water hammer is the pressure surge created when flow is stopped abruptly and the moving column of water is forced to change velocity. An arrestor contains a trapped cushion of gas behind a piston or bladder that compresses and absorbs the shock wave.

Question 44Water Supply and Distribution

Which type of copper tube has the heaviest wall and is the type normally specified for underground water service?

  1. Type M
  2. Type L
  3. Type DWV
  4. Type K Correct answer.

Explanation

Copper tube is produced in named wall thicknesses: Type K is the heaviest, Type L is medium, and Type M is light. Because of its greater wall thickness and resistance to external damage and corrosion, Type K is the standard choice for underground service lines.

Question 45Water Supply and Distribution

Buried water service piping is required to be installed below the local frost line primarily for which reason?

  1. To allow thermal expansion
  2. To reduce water hammer
  3. To increase flow rate
  4. To prevent freezing Correct answer.

Explanation

Frost penetration into soil can reach depths where a shallow water line will freeze and burst. Burying the service below the established frost depth keeps the pipe in unfrozen ground, which is why the burial depth requirement varies by region.

Question 46Water Supply and Distribution

Which valve is the best choice for isolating a water line where the valve will be either fully open or fully closed and pressure loss must be minimized?

  1. A gate valve Correct answer.
  2. An angle valve
  3. A needle valve
  4. A globe valve

Explanation

A gate valve raises a disc out of the flow path, leaving a straight, unobstructed bore when fully open, so friction loss is very low. This makes it a good isolating valve, but its disc can be damaged if it is used to throttle flow.

Question 47Water Supply and Distribution

What does a water meter installed on a building service measure?

  1. Residual pressure in pounds per square inch
  2. Water temperature in degrees Fahrenheit
  3. Velocity of flow in feet per second
  4. Volume of water used Correct answer.

Explanation

A water meter is a volume-measuring device; displacement and turbine meters register the quantity of water that has passed through them, usually in gallons or cubic feet. Velocity and pressure are separate measurements made with different instruments.

Question 48Water Supply and Distribution

In water distribution sizing, what does the abbreviation WSFU stand for?

  1. Water storage fill unit
  2. Water service flow unit
  3. Waste stack fixture unit
  4. Water supply fixture unit Correct answer.

Explanation

A water supply fixture unit is a weighted value assigned to each fixture type that reflects its probable peak demand for cold and hot water. The values are totaled for a branch, riser, or service and then converted to gallons per minute using the code sizing tables.

Question 49Water Supply and Distribution

A building has a reduced pressure zone assembly at the service entrance and a tankless water heater with no other thermal expansion control. What must be added to protect the plumbing system?

  1. A second check valve
  2. A thermal expansion tank Correct answer.
  3. A recirculating pump
  4. A larger water meter

Explanation

A backflow assembly contains check valves that make the system closed, so water expanded by heating has nowhere to go and pressure can rise sharply. A thermal expansion tank with a precharged air cushion absorbs that increased volume and keeps pressure within safe limits.

Question 50Water Supply and Distribution

Which backflow prevention assembly is required for a high-hazard connection where both backsiphonage and backpressure conditions can occur?

  1. A pressure vacuum breaker
  2. An atmospheric vacuum breaker
  3. A double check valve assembly
  4. A reduced pressure zone assembly Correct answer.

Explanation

A reduced pressure zone assembly has two independently acting check valves with a relief valve between them that discharges if differential pressure is lost. This design protects against both backsiphonage and backpressure and is approved for high-hazard installations.