Other Skilled Trades Pipefitting and Plumbing 2 — Questions and Answers
Question 1: What type of fitting is used to join copper pipe using heat?
- Compression fitting
- Sweat (solder) fitting (Correct answer)
- Flare fitting
- Push-connect fitting
Correct answer: Sweat (solder) fitting
Sweat fittings (also called solder fittings) are the traditional method for joining copper pipe — the joint is heated with a torch and solder is drawn into the fitting by capillary action.
Question 2: What is the function of a pressure relief valve (PRV) on a water heater?
- To regulate incoming water pressure
- To relieve excess pressure or temperature to prevent tank explosion (Correct answer)
- To mix hot and cold water
- To prevent backflow into the supply line
Correct answer: To relieve excess pressure or temperature to prevent tank explosion
The T&P (temperature and pressure) relief valve opens automatically if pressure or temperature in the water heater exceeds safe limits, venting water/steam to prevent a catastrophic tank failure.
Question 3: What is the difference between black iron pipe and galvanized pipe in plumbing?
- They are identical products with different brand names
- Black iron has no zinc coating and is used for gas; galvanized is zinc-coated and used for water supply (Correct answer)
- Black iron is used for hot water; galvanized for cold water
- Black iron is plastic; galvanized is metal
Correct answer: Black iron has no zinc coating and is used for gas; galvanized is zinc-coated and used for water supply
Black iron pipe has no protective coating and is used for gas lines, while galvanized pipe is coated with zinc for corrosion resistance and is used for water supply (though rarely in new construction).
Question 4: How many fixture units does a standard toilet contribute to a building drain system per the IPC?
- 1 fixture unit
- 3 fixture units
- 4 fixture units (Correct answer)
- 6 fixture units
Correct answer: 4 fixture units
Per the International Plumbing Code, a residential toilet contributes 4 drainage fixture units (DFU) to the drain system for sizing purposes.
Question 5: What is a 'union' fitting used for in a piping system?
- To connect two pipes of different materials
- To allow a section of pipe to be disconnected and reconnected without cutting the pipe (Correct answer)
- To increase water pressure
- To reduce pipe diameter
Correct answer: To allow a section of pipe to be disconnected and reconnected without cutting the pipe
A union fitting allows two pipe sections to be easily separated and reconnected without cutting, making it essential for equipment that may need future servicing or removal.
Question 6: What test is performed on a newly installed DWV (drain-waste-vent) system to check for leaks before closing walls?
- Hydrostatic pressure test
- Air pressure test or water test (ball test) (Correct answer)
- Smoke test
- Dye test
Correct answer: Air pressure test or water test (ball test)
The standard DWV rough-in test involves plugging all openings and filling the system with water (or pressurizing with air) to verify there are no leaks before walls are closed.
Other Skilled Trades Pipefitting and Plumbing 2
What type of fitting is used to join copper pipe using heat?