Free OK-PLB Practice Questions

Question 1

After a check valve is added at a building's water service, a plumber investigates recurring pressure increases. With the fixtures closed, pressure is initially 58 psi. It gradually reaches 104 psi as the storage water heater reheats, then returns to 58 psi when a faucet opens. No quick-closing valve operates during the pressure rise. Which condition best explains this pattern?

Accepted Answer

The closed water system lacks effective thermal-expansion control.

Answer

A partly closed supply valve is causing excessive friction loss.

Answer

A quick-closing fixture valve is transmitting water hammer through the building.

Answer

The incoming supply pressure remains continuously above the 80-psi limit.

Question 2

A 2-inch sink trap arm has a developed length of 6 feet before its dry-vent connection. A level survey measures 2-3/4 inches of total fall over that run. The sink drains freely during a water test, and the vent takeoff is otherwise correctly installed. Which revision addresses the trap-arm defect?

Accepted Answer

Reduce the fall before the vent by regrading the arm or moving the vent upstream.

Answer

Enlarge the dry vent while retaining the trap arm's existing length and total fall.

Answer

Increase the trap-arm slope to 1/2 inch per foot to improve its scouring action.

Answer

Move the vent farther downstream to provide a longer straight run after the trap.

Question 3

A new common gas trunk will supply a furnace rated at 120,000 Btu/h input and a water heater rated at 60,000 Btu/h input. The longest developed path from the meter to either outlet is 37 feet. Use the longest-length method and a gas heating value of 1,000 Btu/ft³.

The applicable Schedule 40 metallic-pipe table is for natural gas with specific gravity 0.60, inlet pressure below 2 psi, and a permitted pressure drop of 0.5 inch water column. Capacities are in cubic feet per hour:
30-ft row: 1/2 inch = 95; 3/4 inch = 199; 1 inch = 374; 1-1/4 inches = 768.
40-ft row: 1/2 inch = 81; 3/4 inch = 170; 1 inch = 320; 1-1/4 inches = 657.

What is the smallest listed size for the common trunk before the appliance branches separate?

Accepted Answer

1-inch pipe

Answer

1/2-inch pipe

Answer

3/4-inch pipe

Answer

1-1/4-inch pipe

Question 4

On a project governed by Oklahoma's amendments to the 2018 IPC, a new PVC drainage section completes a water test. All piping subject to the minimum-head requirement remains under at least 6 feet of water head for 20 minutes, every joint is tight, and the required overlap with the preceding tested section is included. What should the plumber conclude about this section's pressure test?

Accepted Answer

The completed water test satisfies the required test head and holding time.

Answer

The section must be retested under at least 10 feet of water head before acceptance.

Answer

A separate 2.5-psi air test must follow to confirm that the PVC joints are tight.

Answer

The test must continue for 30 minutes because PVC requires a longer holding period.

Question 5

A hotel renovation retains ordinary two-handle shower mixing valves that do not compensate for supply changes. A central ASSE 1017 mixing valve limits the hot-water distribution temperature to 120°F. The contractor proposes relying on that central valve for all shower protection. What is required at each individual shower?

Accepted Answer

Install an ASSE 1016 automatic compensating valve with its maximum setting limited to 120°F.

Answer

Retain the two-handle valve because the ASSE 1017 device already limits the distribution temperature.

Answer

Lower the storage-water-heater thermostat to 120°F and retain the noncompensating shower valve.

Answer

Install an ASSE 1070-only temperature limiter without adding an automatic compensating shower valve.

Question 6

The following schematic represents a drainage isometric. J1 and J2 are fixture-branch connections into one vertical soil stack. Segment X is above J2, the highest drainage connection, and continues to the open roof terminal. No other fixture connects to X.

Open roof terminal
    |
    X
    |
    J2 <-- Upper-floor fixture drains
    |
    J1 <-- Lower-floor fixture drains
    |
To building drain

Which designation belongs on segment X in the piping takeoff?

Accepted Answer

Stack vent

Answer

Vent stack

Answer

Branch vent

Answer

Wet vent

Question 7

Two plumbers are working in an unshored sewer trench 4-1/2 feet deep, with a ladder 15 feet away. After a rain shower, the competent person sees new tension cracks and soil sloughing beside their work area. One worker argues that the trench is too shallow to require cave-in protection. What must happen first?

Accepted Answer

Remove the workers from the hazardous area until adequate protective measures are in place.

Answer

Keep a spotter at the edge while the plumbers finish because the trench is less than 5 feet deep.

Answer

Move the ladder closer and continue the connection while the competent person watches the cracks.

Answer

Have the plumbers install shoring against the affected wall before they leave the trench.

Question 8

A lawn-irrigation system supplied from potable water is being fitted with a fertilizer injector and a downstream booster pump. The pump can create backpressure, and downstream valves can keep the line pressurized between irrigation cycles. Which assembly is suitable for this connection under Oklahoma's 2018 IPC requirements?

Accepted Answer

An ASSE 1013 reduced-pressure-principle assembly

Answer

An ASSE 1015 double-check valve assembly

Answer

An ASSE 1020 pressure vacuum breaker assembly

Answer

An ASSE 1056 spill-resistant vacuum breaker assembly

Question 9

For a 2-inch PVC drainage joint, a cement label describes a primerless procedure for certain small, nonpressure applications. The work is governed by Oklahoma's amendments to the 2018 IPC. Which joining procedure satisfies the state's requirement?

Accepted Answer

Apply purple primer followed by compatible PVC solvent cement that is not purple.

Answer

Apply clear primer and compatible PVC cement so the completed joint remains free of purple markings.

Answer

Apply compatible cement without primer because the pipe is smaller than 4 inches and carries no pressure.

Answer

Abrade the pipe and socket surfaces, then apply compatible cement without a separate primer coat.

Question 10

A new building has a basement finished-floor elevation of 96.0 feet and a ground-floor elevation of 104.0 feet. The next upstream public-sewer manhole cover is at elevation 100.0 feet. Both floors can drain to the sewer by gravity. How should their drainage branches be arranged for backwater protection?

Accepted Answer

Protect the basement branch with a backwater valve; join the ground-floor branch downstream of that valve.

Answer

Join both floor branches upstream of one backwater valve installed in the common building drain.

Answer

Protect the ground-floor branch with a backwater valve; connect the basement branch downstream of it.

Answer

Install a backwater valve in each floor's branch, then join the two protected branches before the sewer.

Free OK-PLB Practice Questions

Domain 1: General Plumbing Knowledge and Regulations

Question 1

Domain 2: Piping, Valves, and Control Valves

Question 2

Domain 3: Fixtures and Equipment

Question 3

Domain 4: Water Supply

Question 4

Question 5

Domain 5: Drains and Sewers

Question 6

Domain 6: Vents

Question 7

Domain 8: Isometric Analysis

Question 8

Domain 9: Fuel Gas

Question 9

Domain 10: Safety

Question 10

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