Install a natural gas line in a home using black iron pipe. Cut all pipes to the proper length, thread them, and use the appropriate connectors for installing the new line. Ream any cut pipes to maintain the internal diameter and flow rate. Install a shutoff valve for each appliance you are installing.
Before beginning installation, check local codes to determine if they allow you to run the line for yourself. In Seattle, for example, homeowners can install gas lines in their own properties but cannot install them for other property owners without a license.
Determine the correct size pipe by consulting a gas flow chart. Longer pipes require a larger inside diameter to provide the same amount of pressure at the appliance. Appliances that provide more heat require larger pipes than those that provide less heat.
Test the system before use. Use a mechanical gauge, and apply air pressure to 1.5 times the line's working pressure. It should maintain the pressure for a minimum of 10 minutes. If the pressure leaks, use a solution of soap and water at the joints to locate and repair leaks before connecting to the natural gas supply. Never test for gas leaks using an open flame.