Iron and steel are more economical than stainless steel. They are compatible and can be used interchangeably.

Brass and bronze have good corrosion resistance. They are often used in drinking water and plumbing applications. Brass and bronze are compatible and can be used interchangeably.

Plastic pipe and pipe fittings are lighter in weight than metal pipe and pipe fittings. They are typically for low- to medium-pressure applications up to 1,000 psi.