Other Skilled Trades Pipefitting and Plumbing 1 — Questions and Answers
Question 1: What is the minimum slope required for a residential drain pipe to ensure proper drainage per the IPC/UPC?
- 1/16 inch per foot
- 1/8 inch per foot
- 1/4 inch per foot (Correct answer)
- 1/2 inch per foot
Correct answer: 1/4 inch per foot
The International Plumbing Code requires a minimum slope of 1/4 inch per foot (2%) for drain lines 3 inches or less in diameter to ensure solids flow properly.
Question 2: What does the acronym PEX stand for in plumbing?
- Polyethylene Expanded
- Cross-Linked Polyethylene (Correct answer)
- Pressure Exchange pipe
- Polymer Extruded Cross-section
Correct answer: Cross-Linked Polyethylene
PEX stands for Cross-Linked Polyethylene, a flexible plastic tubing widely used in residential water supply systems for its freeze resistance and ease of installation.
Question 3: What is the purpose of a P-trap in a plumbing drain system?
- To increase water pressure at fixtures
- To hold a water seal that prevents sewer gases from entering the building (Correct answer)
- To filter debris from the drain line
- To allow for pipe expansion and contraction
Correct answer: To hold a water seal that prevents sewer gases from entering the building
A P-trap holds a water plug in its curved section that acts as a seal, blocking sewer gases from traveling back through the drain and into occupied spaces.
Question 4: Which pipe material requires the use of solvent cement (glue) for joining?
- Copper pipe
- Galvanized steel pipe
- PVC and CPVC pipe (Correct answer)
- PEX tubing
Correct answer: PVC and CPVC pipe
PVC and CPVC pipes are joined using solvent cement, which chemically welds the plastic surfaces together to form a permanent, watertight bond.
Question 5: What is the standard residential hot water temperature set point recommended by the US Department of Energy to balance scald prevention and Legionella control?
- 100°F
- 110°F
- 120°F (Correct answer)
- 140°F
Correct answer: 120°F
120°F is the recommended water heater set point — it prevents most scalding incidents while being hot enough to inhibit Legionella bacteria growth for most residential applications.
Question 6: What does 'water hammer' refer to in a plumbing system?
- A type of pipe fitting tool
- A pressure surge caused by the sudden stopping of flowing water (Correct answer)
- Low water pressure in the system
- Banging pipes due to inadequate support
Correct answer: A pressure surge caused by the sudden stopping of flowing water
Water hammer is a pressure wave (hydraulic shock) that occurs when flowing water is suddenly stopped, such as when a fast-closing valve shuts, causing a loud banging noise and potentially damaging pipes.
Other Skilled Trades Pipefitting and Plumbing 1
What is the minimum slope required for a residential drain pipe to ensure proper drainage per the IPC/UPC?