Cast Iron (CI) pipes are widely used in various applications like water supply, drainage, and sewage systems. Understanding their properties, including their advantages and disadvantages, is crucial for selecting the right material for specific engineering projects. The question asks to identify which statement is NOT an advantage of CI pipes. Let's analyze each given option.

Cast Iron Pipes Cost

One of the notable features of CI pipes is their cost-effectiveness. Compared to some other materials, they offer a good balance of durability and price. Therefore, the statement that CI pipes are of moderate cost is generally considered an advantage, especially for large-scale infrastructure projects. This makes them an economical choice in many scenarios.

Corrosion Resistance of CI Pipes

Cast iron pipes are known for their inherent resistance to corrosion, particularly when exposed to water and various soil conditions. This natural resistance helps in ensuring a longer service life, reducing the need for frequent replacements or extensive maintenance. Thus, being resistant to corrosion is a significant advantage of CI pipes, contributing to their durability and reliability over time.

Jointing Ease for CI Pipes

The ease of jointing for CI pipes can vary depending on the type of joint used. Older methods, such as lead-caulked bell-and-spigot joints, were often labor-intensive and required skilled workers. However, modern CI pipe systems frequently use push-on or mechanical joints which are designed to be quicker and easier to install. While modern jointing methods have improved, traditionally, the jointing of cast iron pipes was not always considered 'easier' compared to very simple modern pipe connections like solvent welding for plastics. However, this is not their primary or most significant disadvantage when considering all aspects.

Fragility of CI Pipes

This is the most critical point for this question. Cast iron is a type of iron alloy known for its high compressive strength but relatively low tensile strength and ductility. This characteristic makes cast iron pipes inherently brittle or fragile. They are susceptible to cracking or breaking if subjected to sudden impacts, excessive bending stress, or uneven ground settlement. Therefore, the statement "They are not fragile" is factually incorrect regarding the material properties of CI pipes. Since CI pipes are indeed fragile, this property is a disadvantage, not an advantage. Consequently, the claim that they are "not fragile" is NOT an advantage; it describes a non-existent positive trait or denies a real negative trait.

CI Pipes Advantages Summary

Based on the analysis, the statement that is NOT an advantage of CI pipes is the claim of them being "not fragile". In reality, cast iron pipes are known for their brittleness, which is a significant limitation or disadvantage in certain applications where flexibility or impact resistance is required.