Final answer:
The major advantage of PVC in replacing cast iron for plumbing applications is that PVC is a more durable and corrosion-resistant material.
Step-by-step explanation:
The major advantage of PVC in replacing cast iron for plumbing applications is that PVC is a more durable and corrosion-resistant material. Unlike cast iron, PVC pipes do not rust or corrode, which extends their lifespan and reduces maintenance costs. PVC pipes are also lighter in weight and easier to install, making them a more convenient choice for plumbers.