What Is a Supply Line?

A plumber working on the supply line to a toilet.

Supply lines are what bring water or gas to your home's appliances and fixtures from the permanent pipes behind the walls. Supply lines for gas appliances such as ovens, fire places, and clothes dryers are typically made of copper or stainless steel with a plastic coating. Supply lines for water applications are typically made of copper or flexible plastic. The supply lines may need to be replaced from time to time due to leaking or other such damage, but are available at home improvement stores.