PC Plumber Pipe Installation & Repair 3 — Questions and Answers
Question 1: When transitioning from copper pipe to CPVC pipe, which fitting must be used to prevent a chemical reaction between the two materials?
- A standard copper coupling
- A dielectric union
- A copper-to-CPVC transition fitting (Correct answer)
- A PVC bushing
Correct answer: A copper-to-CPVC transition fitting
Dedicated copper-to-CPVC transition fittings are required because CPVC solvent cement is incompatible with copper and direct connections can fail.
Question 2: What is the maximum allowable temperature for CPVC hot water supply pipe according to most plumbing codes?
- 140°F
- 160°F
- 180°F (Correct answer)
- 200°F
Correct answer: 180°F
CPVC is rated for continuous use up to 180°F, making it suitable for residential hot water supply lines.
Question 3: A plumber is running PEX tubing through a wall cavity. Which tool is used to expand the PEX end before inserting an expansion fitting?
- PEX crimping tool
- PEX expansion tool (Correct answer)
- Pipe reamer
- Pipe flaring tool
Correct answer: PEX expansion tool
A PEX expansion tool (used with expansion fittings) enlarges the pipe end so it can be pushed over the fitting and then contracts to form a leak-tight seal.
Question 4: Under the IPC, what is the minimum pipe size for a water service line supplying a single-family residence?
- 1/2 inch
- 3/4 inch (Correct answer)
- 1 inch
- 1-1/4 inch
Correct answer: 3/4 inch
The IPC requires a minimum 3/4-inch water service pipe for a single-family dwelling to ensure adequate flow and pressure.
Question 5: What condition causes PVC pipe to expand and potentially crack if installed without expansion loops or offsets in long horizontal runs?
- High water pressure
- Thermal expansion (Correct answer)
- Chemical degradation
- UV exposure
Correct answer: Thermal expansion
PVC has a high coefficient of thermal expansion, so long runs must include offsets or expansion loops to absorb movement and prevent cracking.
Question 6: Which threading standard is used for most plumbing pipe threads in the United States?
- BSP (British Standard Pipe)
- NPT (National Pipe Taper) (Correct answer)
- Metric ISO threads
- UNF (Unified National Fine)
Correct answer: NPT (National Pipe Taper)
NPT (National Pipe Taper) is the standard tapered thread form used on pipe and fittings throughout US plumbing systems.
Question 7: When pressure testing a newly installed potable water system, what is the standard test pressure and duration specified by most plumbing codes?
- 50 psi for 15 minutes
- 100 psi for 15 minutes (Correct answer)
- 150 psi for 30 minutes
- 80 psi for 60 minutes
Correct answer: 100 psi for 15 minutes
Most plumbing codes require a hydrostatic test at 100 psi held for a minimum of 15 minutes without pressure loss.
PC Plumber Pipe Installation & Repair 3
When transitioning from copper pipe to CPVC pipe, which fitting must be used to prevent a chemical reaction between the two materials?