What material is commonly used for water supply pipes according to plumbing codes?

Water supply pipes can be made from a variety of materials, and all options listed—steel, copper, and plastic (PVC)—are commonly used in plumbing systems as per national plumbing codes.

Steel pipes offer durability and strength and are often utilized in situations where high pressure is a factor, though they may be subject to rust and corrosion over time. Copper piping is known for its excellent corrosion resistance and antibacterial properties, which makes it favorable for potable water systems. It can withstand high temperatures and is often used in residential plumbing. Plastic pipes, particularly PVC, are lightweight, resistant to corrosion, and easy to install, making them an attractive option for many plumbing applications, especially for drainage and venting.

Since each of these materials has distinct advantages depending on the context of their use, they all fit within the regulations set out in the plumbing codes. This versatility is why the correct answer encompasses all of them, illustrating that plumbing codes allow for various options to meet different requirements in water supply systems.