Master Plumber Exam Water Heaters and Hot Water Systems 2 — Questions and Answers
Question 1: What type of anode rod is recommended for a water heater connected to a water softener system?
- Magnesium anode rod
- Aluminum-zinc combination anode rod (Correct answer)
- Copper anode rod
- Titanium anode rod
Correct answer: Aluminum-zinc combination anode rod
Aluminum-zinc anode rods are preferred for softened water because magnesium rods corrode too rapidly in the elevated-conductivity environment created by salt-based softeners.
Question 2: Per the International Plumbing Code, what is the maximum hot water temperature permitted at bathing fixtures in healthcare facilities?
- 100°F
- 110°F (Correct answer)
- 120°F
- 130°F
Correct answer: 110°F
The IPC limits hot water at healthcare bathing fixtures to 110°F to protect patients who may have reduced sensation, mobility, or reaction time from scalding injuries.
Question 3: A tankless water heater must deliver 2.5 GPM with a 70°F temperature rise. Approximately how many BTU/hr must it produce?
- 52,500 BTU/hr
- 87,500 BTU/hr (Correct answer)
- 105,000 BTU/hr
- 140,000 BTU/hr
Correct answer: 87,500 BTU/hr
BTU/hr = GPM × 60 min × 8.33 lb/gal × ΔT = 2.5 × 60 × 8.33 × 70 ≈ 87,465 BTU/hr.
Question 4: According to the Uniform Plumbing Code, what is the maximum height above the floor or flood-level rim of a floor drain at which a T&P relief valve discharge pipe may terminate?
- 2 inches
- 4 inches
- 6 inches (Correct answer)
- 12 inches
Correct answer: 6 inches
The UPC requires the T&P discharge pipe to terminate no more than 6 inches above the floor or drain flood-level rim so hot water discharges safely without risk of scalding nearby occupants.
Question 5: What does the Energy Factor (EF) rating measure for a water heater?
- The maximum water temperature the heater can reach
- The overall energy efficiency based on a simulated 24-hour use cycle (Correct answer)
- The recovery rate in gallons per hour at a 100°F rise
- The standby heat loss in BTU per hour
Correct answer: The overall energy efficiency based on a simulated 24-hour use cycle
The EF rating compares the energy content of hot water delivered to total energy consumed over a standardized 24-hour test cycle, representing overall efficiency.
Question 6: Which venting material is NOT approved for use as a connector on a Category I atmospheric gas water heater?
- Type B double-wall vent pipe
- Single-wall galvanized steel connector
- Flexible aluminum dryer duct (Correct answer)
- Listed stainless steel flue liner
Correct answer: Flexible aluminum dryer duct
Flexible aluminum dryer duct is not listed for gas appliance venting because it cannot withstand the temperature and corrosion requirements for flue gas exhaust.
Question 7: What is the minimum required slope for a T&P relief valve discharge pipe to ensure complete self-drainage?
- 1/8 inch per foot
- 1/4 inch per foot (Correct answer)
- 1/2 inch per foot
- 1 inch per foot
Correct answer: 1/4 inch per foot
T&P discharge pipes must slope downward at a minimum 1/4 inch per foot so water drains completely and does not pool in the pipe between relief events.
Master Plumber Exam Water Heaters and Hot Water Systems 2
What type of anode rod is recommended for a water heater connected to a water softener system?