AZ C-37 (CR-37) Plumbing Contractor Exam Study Guide Questions And Correct Answers (Verified Solutions) | Newest Update 2026/2027 | Graded A+ | 100% Assured Pass.

AZ C-37 (CR-37) Plumbing Contractor Exam Study Guide Questions And Correct Answers (Verified Solutions) | Newest Update 2026/2027 | Graded A+ | 100% Assured Pass. . What is the primary purpose of a trap in a plumbing fixture? A) To filter debris from wastewater B) To prevent sewer gases from entering the building C) To regulate water flow D) To reduce water consumption Rationale: A trap maintains a water seal that blocks sewer gases from entering the building, ensuring a sanitary, odor-free interior. 2. Which type of trap is most commonly used under a lavatory sink? A) S-trap B) P-trap C) Drum trap D) Bell trap Rationale: P-traps are the standard under sinks because they reliably maintain a water seal, are easy to clean and maintain, and comply with modern plumbing code requirements. 3. In a drainage system, what is the purpose of a vent pipe? A) To carry waste to the sewer B) To provide a path for heat to escape C) To filter waste before disposal D) To allow fresh air into the system to prevent vacuum formation and prevent siphoning of traps Rationale: Vent pipes equalize air pressure in drain-waste-vent (DWV) systems, preventing trap siphonage and allowing wastewater to flow smoothly. 4. Which material is most suitable for drainage-waste-vent (DWV) piping in many plumbing installations? A) PVC B) ABS C) Cast iron D) Copper Rationale: Cast iron is durable, handles heat well, and is commonly used in commercial or heavy-duty DWV systems — especially where rigidity and fire-resistance matter. 5. What is the function of a cleanout in a drainage system? A) To prevent backflow of waste into the fixture B) To provide access for cleaning and maintaining the drainage system C) To allow connection of additional fixtures D) To filter waste before disposal Rationale: Cleanouts provide maintenance access so blockages or buildup can be cleared — essential for maintaining system function over time. 6. What is the typical slope required for a horizontal drainage pipe to ensure proper flow? A) Level / no slope B) 1/16 inch per foot C) 1/8 inch per foot D) 1/2 inch per foot Rationale: A slope of 1/8 inch per foot is generally acceptable for gravity-assisted flow without excessive velocity or risk of siphoning. 7. Which of the following is true about the function of a vented trap? A) It prevents waste from entering the system. B) It connects the drain and vent systems to prevent siphoning of the trap. C) It is used only for kitchen sinks. D) It is only used at toilets. Rationale: A vented trap connects both to the drain and vent system, enabling proper air equalization to maintain the trap seal during discharge. 8. In a plumbing installation, what is a “combination waste and vent” system? A) A system that separates drainage and venting B) A system that uses a single pipe for both drainage and venting C) A system that filters waste before venting D) A system that uses electrical pumps for waste flow Rationale: Combination waste-and-vent systems are designed to use a single pipe for both waste flow and venting — common in compact installations or where separate vent piping is impractical. 9. What is the minimum diameter commonly used for a residential bathroom sink (lavatory) drain line under typical plumbing code? A) 1 inch B) 1.25 inches C) 1.5 inches D) 2 inches Rationale: A 1.5-inch drain line gives adequate capacity for typical sink waste water flow and is widely accepted under plumbing codes for lavatories. 10. Which type of piping material is commonly used for venting purposes? A) CPVC B) ABS C) Copper D) PVC Rationale: PVC is widely used for vent piping because of its durability, ease of installation, resistance to corrosion, and suitability for venting gases. 11. What is the primary purpose of a backflow prevention device in a potable water supply system? A) To filter debris from water B) To regulate water pressure C) To increase water flow D) To prevent contaminated water from flowing back into the potable water supply Rationale: Backflow preventers protect drinking water by ensuring waste or non-potable water cannot reverse-flow into the clean water supply. protection while being simpler and less costly than RPZ systems. 12. What is the standard minimum size for a toilet drain line in most plumbing systems? A) 2 inches B) 3 inches C) 4 inches D) 5 inches Rationale: A 3-inch drain line provides sufficient capacity for waste discharge from toilets while preventing clogging or overflow. 13. What is the purpose of an indirect waste system (such as for a dishwasher or ice-maker)? A) To allow waste to flow directly into potable water supply B) To filter wastewater before disposal C) To discharge wastewater indirectly into a drain or receptor, preventing backflow contamination D) To reuse wastewater for other fixtures Rationale: Indirect waste systems keep potentially contaminated water from food prep or appliances separate from potable water or main drains, reducing sanitary and contamination risks. 14. Where should the air gap of an indirect waste discharge be located relative to the flood-level rim of the receiving fixture? A) At floor level B) At least 1 inch above the flood level rim C) At the trap outlet D) Below the rim Rationale: An air gap ensures physical separation between wastewater discharge and the fixture, preventing backflow into potable or clean systems. 15. What type of piping is commonly used for water supply systems in modern plumbing installations? A) Galvanized steel B) Cast iron C) PEX or CPVC or PVC D) Clay Rationale: PEX, CPVC, and PVC are widely used due to flexibility, corrosion resistance, ease of installation, and code acceptance in many jurisdictions. 16. Which backflow prevention device is commonly used in commercial or industrial applications with high contamination hazard? A) Air gap B) Double check valve assembly (DCVA) C) Reduced pressure zone (RPZ) valve D) Atmospheric vacuum breaker (AVB) Rationale: RPZ valves provide the highest level of protection against back-pressure and back-siphonage, suitable where water contamination risks are significant. 17. For lower-risk plumbing applications (e.g., standard residential supply), which backflow prevention device may be adequate? A) RPZ valve B) Pressure vacuum breaker C) Double check valve assembly (DCVA)