Why are cast iron (CI) pipes historically favored in water-supply distribution systems?

Introduction / Context:
Material selection for water distribution mains has evolved, but cast iron and later ductile iron have long been standards due to their mechanical robustness and service longevity. Understanding historical reasons helps when interpreting legacy systems and making rehabilitation plans.

Given Data / Assumptions:

• Buried distribution mains under traffic and soil loads.
• Pressures typical of municipal networks.
• Compatibility with joints and fittings of the time.

Concept / Approach:
CI provides good ring stiffness and compressive strength to withstand burial conditions. Mechanical joints, flanges, and bell-and-spigot connections eased installation. With protective linings and coatings, CI achieved good durability and relatively low maintenance for decades.

Step-by-Step Solution:

Verification / Alternative check:
Many cities still operate CI mains installed in the early to mid-20th century, demonstrating durability under proper corrosion control.

Why Other Options Are Wrong:
Each individual benefit is valid; a comprehensive view recognizes all listed advantages.

Common Pitfalls:
Confusing CI with ductile iron (DI); modern replacements often prefer DI or HDPE depending on conditions, but the historical rationale for CI remains solid.

Final Answer:
all the above.