100+ Free AZ ROC C-37 Plumbing (Commercial) Practice Questions

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Key Facts: AZ ROC C-37 Plumbing (Commercial) Exam

100 Questions

Official Question Count

PSI Candidate Information Bulletin

240 Minutes

Time Limit

PSI Candidate Information Bulletin

70%

Passing Score

Arizona Registrar of Contractors

$66

Exam Fee

PSI Services LLC

Open Book Computerized MCQ

Exam Format

PSI / AZ ROC Guidelines

100 Questions

Practice Question Bank

OpenExamPrep Practice Bank

The Arizona ROC C-37/CR-37 Commercial Plumbing Examination consists of 100 scored multiple-choice questions administered in a 240-minute open-book PSI computer test session with a 70% passing requirement ($66 exam fee). This online practice question bank provides 100 realistic English-language practice questions with step-by-step technical explanations and worked code calculations adapted for exam preparation.

Sample AZ ROC C-37 Plumbing (Commercial) Practice Questions

Try these sample questions to test your AZ ROC C-37 Plumbing (Commercial) exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Under the Uniform Plumbing Code (UPC), what is the maximum Drainage Fixture Unit (DFU) capacity for a 4-inch horizontal building drain installed at a slope of 1/4 inch per foot (2% slope)?

A.216 DFU

B.180 DFU

C.256 DFU

D.300 DFU

Explanation: According to UPC Table 703.2 (and IPC Table 710.1(1)), a 4-inch horizontal drainage pipe laid at a slope of 1/4 inch per foot (2% slope) has a maximum capacity of 216 Drainage Fixture Units (DFU). If laid at 1/8 inch per foot, its capacity drops to 173 DFU.

2What is the maximum allowable horizontal distance from the trap weir to the vent fitting for a 2-inch fixture trap arm under standard plumbing code provisions?

A.5 feet 0 inches

B.3 feet 6 inches

C.6 feet 0 inches

D.8 feet 0 inches

Explanation: Under UPC Table 1002.2 (and IPC Table 909.1), the maximum developed length of a 2-inch fixture trap arm from the trap weir to the vent fitting is 5 feet (60 inches). Exceeding this distance creates excess hydraulic drop, increasing the risk of trap siphonage.

3What is the minimum required horizontal slope per foot for drainage piping with a diameter of 2-1/2 inches or smaller?

A.1/4 inch per foot

B.1/8 inch per foot

C.1/2 inch per foot

D.3/4 inch per foot

Explanation: Standard plumbing codes mandate a minimum slope of 1/4 inch per foot (2% grade) for horizontal drainage piping 2-1/2 inches or smaller. This slope ensures adequate scouring velocity (2 feet per second minimum) to prevent solids from settling.

4A commercial building drain cleanout is installed on a 4-inch pipe. What minimum clearance must be provided in front of the cleanout opening for rodding and maintenance access?

A.18 inches

B.12 inches

C.24 inches

D.36 inches

Explanation: Plumbing codes require a minimum clearance of 18 inches in front of cleanouts on pipes 3 inches and larger (and 12 inches for pipes 2 inches and smaller) to allow sewer snake cables and drain cleaning equipment to operate.

5In a commercial restroom battery, what is the maximum number of floor-outlet water closets or fixtures that can be served by a single circuit vent on a horizontal branch drain?

A.8 fixtures

B.6 fixtures

C.4 fixtures

D.12 fixtures

Explanation: Under IPC Section 911 / UPC Section 911, a maximum of 8 fixtures connected to a horizontal branch drain may be circuit vented in a single battery. Relief vents are required if additional branch intervals or drainage stacks connect upstream.

6A plumbing vent terminal extends through a commercial roof. What is the minimum required horizontal distance from the vent terminal to an operable window, door, or air intake opening?

A.10 feet

B.8 feet

C.5 feet

D.15 feet

Explanation: Plumbing vent terminals must terminate at least 10 feet horizontally from any door, window, or mechanical air intake, or be placed at least 3 feet above the top of such openings to prevent sewer gases from entering the building.

7What is the maximum allowable DFU capacity for a 3-inch soil stack serving a 3-story commercial building when the stack serves more than 3 branch intervals?

A.48 DFU

B.36 DFU

C.24 DFU

D.72 DFU

Explanation: Under standard DWV stack sizing tables (IPC Table 710.1(2) / UPC Table 703.2), a 3-inch vertical stack serving more than 3 branch intervals has a maximum total capacity of 48 DFUs (with a maximum of 20 DFUs per single branch interval).

8When a drainage stack in a multi-story building makes a horizontal offset of greater than 45 degrees, where must relief vents be installed?

A.Above and below the offset of the stack

B.Only at the roof terminal of the stack

C.Directly in the horizontal offset section only

D.At the lowest floor fixture trap arm only

Explanation: Off-setting a drainage stack by more than 45 degrees from the vertical creates hydraulic jump and pressure surges. Codes require relief vents to be installed above and below the horizontal offset to equalize pneumatic pressures.

9In an island sink fixture installation utilizing an island loop vent, at what elevation must the return bend of the vent pipe be positioned relative to the fixture flood rim?

A.As high as possible under the island countertop

B.At least 2 inches below the bottom of the sink basin

C.At least 6 inches above the finished floor

D.Flush with the drain outlet of the trap arm

Explanation: Under UPC Section 909 / IPC Section 916, the island loop vent must rise as high as possible beneath the island countertop before making a 180-degree return bend back down to connect into the horizontal drain.

10When an Air Admittance Valve (AAV) is installed to vent a commercial fixture, what is the minimum required distance the AAV must be located above the horizontal branch drain or fixture drain being served?

A.4 inches above the horizontal branch drain or trap arm weir

B.2 inches above the flood level rim

C.12 inches above the finished floor

D.24 inches above the trap weir

Explanation: Under IPC Section 918.4, an AAV must be installed a minimum of 4 inches above the top of the horizontal branch drain or fixture drain being served, and at least 6 inches above flood level rim for stack applications.

About the AZ ROC C-37 Plumbing (Commercial) Exam

The Arizona ROC C-37/CR-37 Plumbing (Commercial) Examination is a 240-minute, open-book computer-administered trade exam managed by PSI Services LLC for the Arizona Registrar of Contractors. It evaluates comprehensive technical knowledge across commercial drainage waste and vent sizing, indirect waste receptors, water supply sizing and backflow protection, storm drainage roof drain flow, plumbing fixture units and water heater venting, interceptor sizing, fuel gas pipe sizing under IFGC/NFPA 54, septic system ADEQ engineering standards, hydronic heating/cooling piping, commercial fire sprinkler system tie-ins, and OSHA excavation/trenching rules.

Questions

100 scored questions

Time Limit

240 minutes

Passing Score

70%

Exam Fee

$66 (Arizona ROC / PSI Services LLC)

AZ ROC C-37 Plumbing (Commercial) Exam Content Outline

15%

Drainage Waste and Vents

Drainage Fixture Unit (DFU) sizing for building drains, stacks, and sewers; horizontal slope requirements; fixture trap arms; relief vents, circuit vents, stack vents, and vent stack sizing; wet venting and air admittance valves under IPC/UPC standards.

Indirect Waste

Air gaps and air breaks for commercial food preparation sinks, dishwashers, ice machines, medical equipment, clear water waste, condensation drains, indirect waste receptors, and trap priming requirements.

12%

Water Supply Systems

Water Supply Fixture Units (WSFU), peak demand gpm calculations (Hunter's Curve), pipe sizing for copper, PEX, CPVC, and steel; water pressure regulation, booster pump systems, thermal expansion tanks, and maximum developed length friction loss.

Backflow Prevention

Cross-connection hazard classifications (high hazard vs low hazard); Reduced Pressure Zone (RPZ) assemblies, Double Check Valve Assemblies (DCVA), Pressure Vacuum Breakers (PVB), atmospheric vacuum breakers, air gaps, and field testing/inspection standards.

Roof Drains and Storm Drainage Systems

Roof drain sizing based on rainfall rate (inches per hour) and horizontal roof area (sq ft); primary and secondary (overflow) roof drain systems, scuppers, vertical conductors, leaders, and underground storm drain piping slope.

Plumbing Fixtures including Water Heaters

Commercial plumbing fixture clearances, ADA accessibility requirements, flushometer valve installations, commercial water heater storage/recovery calculations, thermal expansion control, temperature & pressure (T&P) relief valve piping, and venting.

General Knowledge

Plumbing definitions, code compliance, piping materials and jointing methods, hanger and support spacing, pipe expansion/contraction, sleeve penetrations, firestop assembly details, and hydrostatic/air pressure testing rules.

Specialty Plumbing, Interceptors, and Traps

Grease interceptor sizing (hydromechanical vs gravity), sand/oil interceptors, lint traps, acid neutralization tanks, fixture trap seal protection, deep seal traps, and trap primers.

11%

Fuel Gas

Natural gas and LP-gas pipe sizing (cubic feet per hour / BTU demand) using IFGC / NFPA 54 tables; steel, copper, and CSST gas piping; gas pressure regulators, sediment traps, appliance connections, combustion air, and gas vent clearance.

11%

Septic and Sewer

On-site wastewater treatment systems (ADEQ Engineering Bulletin No. 12), septic tank sizing, percolation rate testing, soil absorption field design, distribution boxes, sewer line slope and cleanout spacing.

Hydronics

Closed and open hydronic heating/cooling piping systems, boiler trim, expansion tanks, air separators, circulator pump head calculations, balancing valves, and glycol anti-freeze solutions.

Fire Sprinklers

Commercial fire protection water supply connections, backflow protection on dedicated fire service lines (DCDA / RPDA), standpipe systems, post indicator valves (PIV), underground fire main installation under NFPA 24, and freeze protection.

Excavation

OSHA 29 CFR 1926 Subpart P safety rules; soil classification (Type A, B, C), protective shoring, sloping, and benching systems; trench access/egress ladder spacing; spoil pile clearance; atmospheric testing; and underground utility locating (Arizona 811).

How to Pass the AZ ROC C-37 Plumbing (Commercial) Exam

What You Need to Know

Passing score: 70%
Exam length: 100 questions
Time limit: 240 minutes
Exam fee: $66

Keys to Passing

Work through all 100 available questions
Review every answer and explanation
Track weak areas and revisit them
Use our AI tutor for tough concepts

AZ ROC C-37 Plumbing (Commercial) Study Tips from Top Performers

1Practice Drainage Fixture Unit (DFU) and Water Supply Fixture Unit (WSFU) sizing tables for building drains, branches, stacks, and water distribution mains.

2Master fuel gas pipe sizing using IFGC/NFPA 54 tables for natural gas (0.60 specific gravity) and propane gas, taking into account developed length and pressure drop.

3Study backflow protection requirements: know when Reduced Pressure Zone (RPZ) assemblies are required versus Double Check Valve Assemblies (DCVA) or Pressure Vacuum Breakers (PVB).

4Understand ADEQ septic tank sizing formulas, soil percolation rates, trench loading rates, and required separation distances from wells and water mains.

5Memorize OSHA 29 CFR 1926 Subpart P trenching rules: protective system depth (5 ft+), ladder spacing (within 25 ft of travel), spoil pile setback (2 ft minimum), and soil classifications.

Frequently Asked Questions

How many questions are on the official Arizona ROC C-37/CR-37 Plumbing Commercial exam?

The official PSI Arizona ROC C-37/CR-37 Commercial Plumbing examination contains 100 scored multiple-choice questions. Candidates are allotted 240 minutes (4 hours) to complete the exam.

What passing score is required for the AZ ROC C-37 exam?

A minimum passing score of 70% (70 correct out of 100 questions) is required to pass the trade examination.

Is the Arizona ROC C-37 Plumbing (Commercial) exam open book?

Yes, the examination is open-book. Approved code books and reference materials—such as the International Plumbing Code / Uniform Plumbing Code, International Fuel Gas Code / NFPA 54, and OSHA 29 CFR 1926—may be brought into the PSI test center.

What topics carry the highest weight on the C-37 commercial plumbing exam?

Drainage Waste and Vents carries the highest weight at 15% (15 questions), followed by Water Supply Systems at 12% (12 questions), Fuel Gas at 11% (11 questions), and Septic and Sewer at 11% (11 questions).

Where can I schedule the AZ ROC C-37 Commercial Plumbing examination?

Examinations are scheduled online through PSI Services LLC at https://test-takers.psiexams.com/azcon or by contacting PSI candidate services.

100+ Free AZ ROC C-37 Plumbing (Commercial) Practice Questions

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