Black pipe is used for the distribution of natural gas both inside the house to fireplaces, stoves and furnaces, as well as outside to the main gas line.
Propane gas is also distributed using black pipe both inside and outside the house. Like natural gas, propane gas is delivered to furnaces, fireplaces and stoves inside the house. The storage line typically goes to a propane supply tank located outside the house.
In homes built before the 1960s black pipe was often used to transport water from either wells or the main water supply line to inside the home. Due to corrosion, however, black pipe has largely been replaced with PVC pipe.
Because of its durability, black pipe is used for hot-water circulation in boiler systems found in businesses, schools and industrial applications.
The oil and petroleum industry use black pipe because of its strength and durability. Black pipe is used at oil refineries, on oil rigs and for offshore refineries.