Journeyman Plumbers Exam Water Heaters and Hot Water Systems 2 — Questions and Answers
Question 1: At what minimum storage temperature is Legionella bacteria effectively inhibited in a hot water system?
- 120°F (49°C)
- 130°F (54°C)
- 140°F (60°C) (Correct answer)
- 110°F (43°C)
Correct answer: 140°F (60°C)
Legionella bacteria are killed at 140°F (60°C); storing domestic hot water at or above this temperature prevents bacterial colonization and growth in the system.
Question 2: What does the 'first-hour rating' (FHR) indicate about a storage water heater?
- The time required to heat a full tank of cold water from 40°F to 120°F
- The total gallons of hot water the unit can deliver in the first hour starting with a full tank (Correct answer)
- The unit's energy efficiency during the first hour of daily operation
- The minimum warranty period required by federal law
Correct answer: The total gallons of hot water the unit can deliver in the first hour starting with a full tank
First-hour rating (FHR) measures how many gallons of hot water a storage water heater can supply per hour when starting with a fully heated tank, indicating its ability to meet peak demand.
Question 3: Which type of water heater venting uses a concentric pipe system to draw combustion air from outside while exhausting combustion gases directly outdoors?
- Type B natural draft venting
- Atmospheric venting with draft hood
- Direct vent (sealed combustion) (Correct answer)
- Power vent with induced draft blower
Correct answer: Direct vent (sealed combustion)
Direct vent (sealed combustion) water heaters use a concentric or two-pipe system that draws all combustion air from outdoors and exhausts gases outside, making them completely independent of indoor air.
Question 4: What is the maximum hot water delivery temperature typically permitted at fixtures in healthcare facilities and nursing homes?
- 120°F
- 110°F (Correct answer)
- 105°F
- 115°F
Correct answer: 110°F
Healthcare facilities typically limit hot water to 110°F at fixture outlets to protect vulnerable patients — including the elderly, infants, and those with reduced sensitivity — from scalding.
Question 5: An atmospheric gas water heater is installed in a confined mechanical room. What is required to ensure safe operation?
- A carbon monoxide detector only
- A dedicated combustion air supply to the confined space (Correct answer)
- An exhaust fan rated for continuous duty
- No additional provisions if the room has a door
Correct answer: A dedicated combustion air supply to the confined space
Atmospheric gas water heaters require adequate combustion air; when installed in a confined space, openings or ducts providing a dedicated combustion air supply from outside or an adjacent unconfined space are required.
Question 6: What is the minimum required diameter of a drain line from a water heater drain pan per most US plumbing codes?
- 1/2 inch
- 3/4 inch (Correct answer)
- 1 inch
- 1-1/4 inch
Correct answer: 3/4 inch
Water heater pan drain lines must be at least 3/4 inch in diameter to carry away water from a leaking or failed water heater quickly and prevent flooding.
Question 7: In which seismic design categories are water heaters typically required to be anchored or strapped to prevent overturning during an earthquake?
- All categories nationwide, regardless of seismic risk
- Only in coastal flood zones
- Seismic Design Categories C, D, E, and F (high seismic risk areas) (Correct answer)
- Only where local jurisdictions adopt special ordinances
Correct answer: Seismic Design Categories C, D, E, and F (high seismic risk areas)
Seismic strapping is required in higher seismic design categories (C through F) to prevent water heaters from tipping during earthquakes, which could rupture gas lines and cause fires or flooding.
Journeyman Plumbers Exam Water Heaters and Hot Water Systems 2
At what minimum storage temperature is Legionella bacteria effectively inhibited in a hot water system?