Journeyman Plumbers Exam Water Heaters and Hot Water Systems 1 — Questions and Answers
Question 1: Where must a temperature and pressure (T&P) relief valve discharge pipe terminate?
- Within 6 inches of the floor (Correct answer)
- Directly into a floor drain
- At least 24 inches above the floor
- Into the cold water supply line
Correct answer: Within 6 inches of the floor
T&P relief valve discharge pipes must terminate within 6 inches of the floor to direct scalding water safely downward away from occupants.
Question 2: What is the purpose of the dip tube in a storage tank water heater?
- To drain sediment from the bottom of the tank
- To direct incoming cold water to the bottom of the tank (Correct answer)
- To measure the internal water temperature
- To prevent backflow into the cold supply line
Correct answer: To direct incoming cold water to the bottom of the tank
The dip tube directs incoming cold water to the bottom of the tank so it does not mix with the hot water at the top, ensuring efficient delivery of hot water.
Question 3: What is the primary purpose of the sacrificial anode rod in a tank-type water heater?
- To improve heating element efficiency
- To filter sediment from the incoming water supply
- To protect the steel tank lining from corrosion through galvanic action (Correct answer)
- To regulate internal water pressure
Correct answer: To protect the steel tank lining from corrosion through galvanic action
The anode rod (typically magnesium or aluminum) corrodes sacrificially through electrochemical action, protecting the steel tank from rust and premature failure.
Question 4: What is the maximum water heater thermostat setting recommended by most US plumbing codes to prevent scalding in residential occupancies?
- 120°F (49°C) (Correct answer)
- 140°F (60°C)
- 110°F (43°C)
- 130°F (54°C)
Correct answer: 120°F (49°C)
Most US plumbing codes recommend setting residential water heater thermostats no higher than 120°F to prevent scalding injuries, especially for children and elderly occupants.
Question 5: At what minimum height above the garage floor must the ignition source of a gas water heater be located?
- 12 inches
- 18 inches (Correct answer)
- 24 inches
- 36 inches
Correct answer: 18 inches
Gas water heater ignition sources must be at least 18 inches above the garage floor to prevent ignition of gasoline vapors, which are heavier than air and pool near the floor.
Question 6: What type of expansion tank is required when a pressure-reducing valve (PRV) or check valve creates a closed water system on the cold water supply?
- Open atmospheric expansion tank
- Closed bladder-type thermal expansion tank (Correct answer)
- In-line pressure relief canister
- No expansion tank is required for closed systems
Correct answer: Closed bladder-type thermal expansion tank
A closed bladder-type thermal expansion tank is required to absorb the increased pressure caused by thermal expansion of water in a closed system, preventing damage to the water heater and piping.
Question 7: What is the minimum diameter of the discharge pipe for a T&P relief valve on a residential storage water heater?
- 1/2 inch
- 3/4 inch (Correct answer)
- 1 inch
- 3/8 inch
Correct answer: 3/4 inch
The T&P relief valve discharge pipe must be at least 3/4 inch in diameter, matching the standard relief valve outlet size, and must not be reduced in size throughout its length.
Journeyman Plumbers Exam Water Heaters and Hot Water Systems 1
Where must a temperature and pressure (T&P) relief valve discharge pipe terminate?