Master Plumber Exam Plumbing Fixtures and Appliances 3 — Questions and Answers
Question 1: Which appliance requires a dedicated CSST or rigid gas supply line with a union or quick-disconnect fitting for service purposes?
- Gas range
- Gas clothes dryer
- Gas water heater
- All of the above (Correct answer)
Correct answer: All of the above
All gas appliances that may require servicing or replacement should have an accessible shutoff and a union or quick-disconnect to allow disconnection without cutting pipe.
Question 2: The maximum distance allowed between the weir of a P-trap and the trap arm connection to the drain stack is governed by the trap-to-vent distance rule. For a 1½-inch trap arm, this distance is typically:
- 2.5 feet
- 3.5 feet (Correct answer)
- 5 feet
- 6 feet
Correct answer: 3.5 feet
For a 1½-inch trap arm, the maximum trap-to-vent distance is generally 3.5 feet per UPC and IPC tables to maintain the trap seal.
Question 3: A water softener drain must discharge through an air gap or air break to a:
- Directly into the sanitary sewer line
- Indirect waste receptor (Correct answer)
- Trap of the nearest fixture
- Gray water system without any air gap
Correct answer: Indirect waste receptor
Water softener backwash must discharge indirectly to an approved receptor to prevent backflow and cross-contamination of the potable supply.
Question 4: What is the purpose of a vacuum breaker on a faucet with a threaded hose connection (sillcock)?
- To regulate water pressure
- To prevent backflow if a hose is submerged in contaminated water (Correct answer)
- To reduce water hammer
- To limit flow rate
Correct answer: To prevent backflow if a hose is submerged in contaminated water
A hose-connection vacuum breaker prevents back-siphonage in case a garden hose is left submerged in a pool, bucket, or chemical solution.
Question 5: When a dishwasher drain connects to a garbage disposal, the high loop or air gap is required to prevent:
- Noise from the disposal
- Dirty water from siphoning back into the dishwasher (Correct answer)
- Excessive water pressure in the drain line
- Grease buildup in the drain
Correct answer: Dirty water from siphoning back into the dishwasher
The high loop or air gap prevents dirty sink water from back-siphoning into the dishwasher tub when the disposal runs or the sink drains.
Question 6: A clothes washer standpipe must extend above the trap weir a minimum of:
- 12 inches
- 18 inches (Correct answer)
- 24 inches
- 36 inches
Correct answer: 18 inches
The standpipe for a clothes washer must extend a minimum of 18 inches above the trap weir to prevent the drain hose from being siphoned into the drain.
Question 7: Which type of water closet bowl is most effective at preventing visible soiling of the bowl interior?
- Wash-down bowl
- Reverse-trap bowl
- Siphon-jet bowl (Correct answer)
- Blowout bowl
Correct answer: Siphon-jet bowl
Siphon-jet bowls have a larger water surface area that covers most of the bowl interior, reducing visible soiling and odor.
Master Plumber Exam Plumbing Fixtures and Appliances 3
Which appliance requires a dedicated CSST or rigid gas supply line with a union or quick-disconnect fitting for service purposes?