The answer to 'water line vs' is that water lines and sewer lines are two distinct plumbing systems with different functions, installation requirements, and maintenance needs. Water lines carry clean, potable water into a home, while sewer lines carry wastewater and sewage out of the home.
Water lines are typically made of copper, PEX (cross-linked polyethylene), or PVC (polyvinyl chloride) piping, and are responsible for delivering water to faucets, appliances, and other fixtures throughout the home. Sewer lines, on the other hand, are usually made of cast iron, PVC, or ABS (acrylonitrile butadiene styrene) piping, and are responsible for carrying waste and wastewater from the home to the municipal sewer system or a septic tank.