PC Material Selection & Properties 2 — Questions and Answers
Question 1: Which pipe material has the highest resistance to chlorine degradation in potable water systems?
- PVC Schedule 40
- CPVC
- Cross-linked polyethylene (PEX) (Correct answer)
- ABS
Correct answer: Cross-linked polyethylene (PEX)
PEX has superior resistance to chlorine degradation compared to other plastic piping materials used in potable water systems.
Question 2: What is the primary reason copper Type M pipe is NOT recommended for aggressive water conditions?
- It is too expensive
- It has the thinnest wall thickness of the copper types (Correct answer)
- It cannot be soldered
- It expands too much with temperature changes
Correct answer: It has the thinnest wall thickness of the copper types
Type M copper has the thinnest wall of the three copper types (K, L, M), making it more susceptible to corrosion failure in aggressive water.
Question 3: Which material is MOST appropriate for a buried sewer lateral subject to heavy vehicular traffic loads?
- SDR 35 PVC
- ABS DWV
- Extra-strength vitrified clay pipe (Correct answer)
- Cast iron service weight
Correct answer: Extra-strength vitrified clay pipe
Extra-strength vitrified clay pipe provides excellent compressive strength and chemical resistance, making it ideal for high-load buried applications.
Question 4: What does the term 'SDR' mean when applied to plastic pipe?
- Standard Diameter Ratio (Correct answer)
- Structural Drain Rating
- System Design Requirement
- Standard Deflection Resistance
Correct answer: Standard Diameter Ratio
SDR stands for Standard Dimension Ratio, which is the ratio of pipe outside diameter to minimum wall thickness.
Question 5: When connecting a copper water line to a galvanized steel pipe, which fitting must be used to prevent corrosion?
- A standard brass coupling
- A dielectric union (Correct answer)
- A sweat-solder fitting
- A push-fit connector
Correct answer: A dielectric union
A dielectric union isolates dissimilar metals electrically to prevent galvanic corrosion at the junction of copper and steel.
Question 6: Which plastic piping material is rated for both hot and cold water and is commonly color-coded red and blue?
- PVC
- ABS
- PEX (Correct answer)
- HDPE
Correct answer: PEX
PEX (cross-linked polyethylene) is commonly manufactured in red for hot and blue for cold water lines and is rated for both applications.
Question 7: Which material is NOT acceptable for gas supply piping inside a residence according to most US codes?
- Black iron pipe
- CSST (corrugated stainless steel tubing)
- Copper tubing (where gas is not LP)
- PVC pipe (Correct answer)
Correct answer: PVC pipe
PVC is not approved for gas supply piping because it is susceptible to damage, UV degradation, and does not meet gas code requirements.
PC Material Selection & Properties 2
Which pipe material has the highest resistance to chlorine degradation in potable water systems?