Download Nebraska National Electrical Code Practice Exam and more Exams Technology in PDF only on Docsity!
Question 1. What is the main function of a trap in a plumbing drainage system? A) To store water B) To prevent sewer gases from entering the building C) To filter debris D) To accelerate drainage Answer: B Explanation: Traps are designed to maintain a water seal, preventing sewer gases from entering occupied spaces. Question 2. Which material is most commonly used for residential DWV (drain, waste, vent) piping today? A) Copper B) Galvanized steel C) PVC D) Lead Answer: C Explanation: PVC is lightweight, durable, and resistant to corrosion, making it ideal for DWV systems. Question 3. What is the recommended minimum slope for horizontal drainage pipes (under 3” diameter) to ensure proper gravity flow? A) 1/8 inch per foot B) 1/4 inch per foot C) 1/2 inch per foot D) 1 inch per foot Answer: B
Explanation: The UPC and most codes recommend a minimum slope of 1/4 inch per foot for pipes under 3 inches. Question 4. Which of the following is a type of vent system that connects at the highest point of a stack and prevents pressure differences? A) Loop vent B) Common vent C) Circuit vent D) Stack vent Answer: D Explanation: Stack vents extend through the roof and help equalize air pressure in the drainage system. Question 5. What is the primary reason for installing cleanouts in a DWV system? A) To increase water pressure B) To access pipes for maintenance and clearing blockages C) To regulate temperature D) To prevent pipe freezing Answer: B Explanation: Cleanouts allow plumbers to clear blockages and maintain the system without dismantling pipes. Question 6. Which device is installed to prevent reverse flow of contaminated water into the potable supply? A) Pressure regulator B) Check valve C) Expansion tank
C) Reducer D) Coupling Answer: C Explanation: Reducers are designed to connect pipes of differing sizes in a straight run. Question 10. What is the main purpose of a vent pipe in a plumbing system? A) Increase water pressure B) Prevent pipe freezing C) Maintain atmospheric pressure and remove sewer gases D) Filter debris Answer: C Explanation: Vent pipes allow air into the system, preventing siphoning of traps and venting gases. Question 11. In a hydronic heating system, what is typically used to transfer heat to the rooms? A) Ducts B) Radiators C) Air handlers D) Electric coils Answer: B Explanation: Hydronic systems use water-filled radiators to transfer heat efficiently. Question 12. What is the required air gap for protecting potable water from contamination at a fixture? A) Twice the pipe diameter B) Three times the pipe diameter
C) Four times the pipe diameter D) Six inches Answer: A Explanation: Most codes require an air gap of at least twice the diameter of the supply pipe. Question 13. Which of the following is NOT a standard pipe material for DWV systems? A) PVC B) Cast iron C) Aluminum D) ABS Answer: C Explanation: Aluminum is not typically used for DWV systems due to corrosion and strength concerns. Question 14. What is the function of a grease interceptor? A) Prevent pipe corrosion B) Trap hair and debris C) Capture fats, oils, and grease before entering the sewer D) Increase water flow Answer: C Explanation: Grease interceptors prevent fats, oils, and grease from clogging the sanitary system. Question 15. Which safety device is required on a boiler to prevent overpressure? A) Expansion tank B) Pressure relief valve
C) Flexible D) Heavy Answer: B Explanation: Piping for potable water must be non-toxic to ensure safe drinking water. Question 19. What color is commonly used for labeling natural gas piping? A) Blue B) Yellow C) Red D) Green Answer: B Explanation: Yellow is the standard color for marking natural gas lines. Question 20. Which method is commonly used for joining copper water lines? A) Solvent welding B) Soldering C) Threading D) Compression fitting Answer: B Explanation: Soldering creates leak-proof joints in copper piping. Question 21. What is the maximum allowable lead content in plumbing fixtures for potable water? A) 0.5% B) 2%
C) 8%
D) 10%
Answer: A Explanation: Federal law requires lead content in wetted surfaces of fixtures to be below 0.5%. Question 22. For proper drainage, what is the maximum number of water closets permitted on a 3-inch horizontal branch? A) 1 B) 2 C) 3 D) 4 Answer: D Explanation: Four water closets is the maximum allowed by most codes on a 3-inch branch. Question 23. What is the main purpose of a boiler expansion tank? A) Increase heating speed B) Absorb water volume changes from thermal expansion C) Reduce fuel consumption D) Trap air Answer: B Explanation: Expansion tanks accommodate expanding water, preventing overpressure. Question 24. What is the recommended minimum height above the flood level rim for an atmospheric vacuum breaker? A) 1 inch
B) Copper C) PVC D) Lead Answer: B Explanation: Copper is durable and highly resistant to corrosion. Question 28. What is the primary hazard in cross-connecting potable and non-potable water systems? A) Low pressure B) Backflow contamination C) High flow D) Pipe freezing Answer: B Explanation: Cross-connections can allow contaminated water to enter the potable supply. Question 29. Which venting method allows multiple fixtures to share a single vent pipe? A) Individual venting B) Wet venting C) Loop venting D) Parallel venting Answer: B Explanation: Wet venting allows multiple fixtures to share one vent. Question 30. In hydronic heating, what is usually installed to remove entrained air from the water? A) Pressure relief valve
B) Air separator C) Expansion tank D) Flow switch Answer: B Explanation: Air separators ensure efficient operation and prevent noise. Question 31. What is the minimum vertical drop for a standpipe for an automatic clothes washer? A) 12 inches B) 18 inches C) 24 inches D) 36 inches Answer: B Explanation: A minimum 18-inch standpipe prevents overflow and siphoning. Question 32. What is the minimum clearance required above a gas vent termination from the roof? A) 6 inches B) 12 inches C) 24 inches D) 36 inches Answer: B Explanation: 12 inches above the roof is the minimum for safe venting. Question 33. What type of pipe support is required for horizontal copper tubing every 6-8 feet? A) Clamps
A) Must terminate at the roof B) Must be directed to a safe location C) Must be connected to the sewer D) Must terminate above the heater Answer: B Explanation: The discharge must be piped to a safe, visible location to prevent injury. Question 37. Which of the following best defines a circuit vent? A) Vent for a single fixture B) Vent serving two traps C) Vent serving multiple fixtures on a branch D) Main stack vent Answer: C Explanation: Circuit vents serve several fixtures on the same horizontal branch. Question 38. Which material is prohibited for use in potable water supply lines? A) CPVC B) Copper C) Lead D) PEX Answer: C Explanation: Lead piping is banned due to health hazards. Question 39. What is the primary function of an oil interceptor in a plumbing system?
A) Remove grease B) Remove oil from wastewater C) Increase water pressure D) Trap sediment Answer: B Explanation: Oil interceptors prevent oil from entering the sewer system. Question 40. What is the minimum water pressure required at the highest fixture in a residential building? A) 15 psi B) 20 psi C) 35 psi D) 50 psi Answer: B Explanation: 20 psi is the minimum required for adequate fixture operation. Question 41. What is the minimum required depth for burying water service piping in Nebraska to prevent freezing? A) 12 inches B) 24 inches C) 36 inches D) 48 inches Answer: C Explanation: 36 inches is the minimum depth to protect against frost penetration.
Question 45. What is the maximum length allowed for a horizontal clothes dryer vent? A) 10 feet B) 15 feet C) 25 feet D) 35 feet Answer: C Explanation: Most codes limit dryer vents to 25 feet to ensure safe venting. Question 46. Which pipe material is recommended for underground gas service? A) Black iron B) Copper C) Polyethylene D) Galvanized steel Answer: C Explanation: Polyethylene is corrosion-resistant and approved for underground gas piping. Question 47. What is the purpose of a union fitting in a pipe system? A) Allow easy disconnection for maintenance B) Increase flow C) Reduce pressure D) Trap debris Answer: A Explanation: Unions allow quick assembly and disassembly of pipes.
Question 48. What is the required minimum temperature for hot water at public lavatories? A) 100°F B) 110°F C) 120°F D) 140°F Answer: B Explanation: 110°F is the minimum temperature for proper sanitation. Question 49. What is the maximum horizontal distance permitted from a fixture trap to its vent? A) 2 feet B) 4 feet C) 6 feet D) 8 feet Answer: B Explanation: Most codes require venting within 4 feet for proper function. Question 50. What is the function of a pressure reducing valve in a water supply system? A) Increase flow B) Prevent backflow C) Lower incoming water pressure D) Remove air Answer: C Explanation: Pressure reducing valves maintain safe, manageable water pressure.
Question 54. Which type of fire sprinkler system uses pipes filled with compressed air or nitrogen? A) Wet pipe B) Dry pipe C) Deluge D) Pre-action Answer: B Explanation: Dry pipe systems fill with water only when activated, using air or nitrogen otherwise. Question 55. What is the minimum trap size for a residential bathtub? A) 1-1/4 inch B) 1-1/2 inch C) 2 inch D) 2-1/2 inch Answer: B Explanation: 1-1/2 inch traps are standard for bathtubs. Question 56. Which code sets requirements for the installation of liquefied petroleum gas systems? A) NFPA 70 B) NFPA 54 C) NFPA 58 D) UPC Answer: C Explanation: NFPA 58 governs the installation of LP gas systems.
Question 57. What is the primary reason for using dielectric unions in water piping? A) Increase flow B) Prevent galvanic corrosion C) Reduce pressure D) Remove air Answer: B Explanation: Dielectric unions separate dissimilar metals, preventing corrosion. Question 58. Which device is required for automatic filling and maintaining pressure in a hydronic system? A) Pressure reducing valve B) Expansion tank C) Air separator D) Backflow preventer Answer: A Explanation: Pressure reducing valves automatically fill and maintain system pressure. Question 59. What is the maximum allowable length for a horizontal vent pipe before requiring an increase in pipe size? A) 10 feet B) 20 feet C) 40 feet D) 100 feet Answer: C Explanation: Vent pipes longer than 40 feet often require increased size to prevent airflow restrictions.
