Things You'll Need
Threading compound and brush
Yellow sealing tape
Soapy water and brush
Gas pipelines in homes are installed using rigid black-coated steel pipes that are threaded at both ends. The pipes come in various lengths, and are joined together with steel couplings and threading compound. Each pipeline is installed section by section, starting at the gas supply source (usually the gas meter or T/elbow joint on an existing line), then working toward the gas appliance. A test must then be carried out to ensure that no joints are leaking.
Turn off the gas at the gas meter. Place a crescent wrench around the nut on the end of the existing flexible gas supply hose that runs from the gas shutoff valve to the gas appliance. Turn the wrench counterclockwise to remove the hose's nut from the shutoff valve.
Place a pipe wrench around the body of the shutoff valve. Turn the wrench's handle to loosen and remove the valve from the end of the existing gas pipeline. Place the wrench around the section of gas pipe that was attached to the shutoff valve. Turn the wrench counterclockwise to remove this first section of gas pipe form its connecting coupling.
Place the wrench around the coupling and turn it counterclockwise to loosen and remove the coupling. Continue in the same way until all pipe sections and couplings are removed to the point where the new gas line route will attach to the existing line.
Brush threading compound around the threads on one end of the new section of gas pipe. Screw this end of the new pipe by hand into the coupling on the end of the existing gas line. Place the pipe wrench around the new gas pipe and turn it clockwise to tighten it to the coupling.
Brush compound around the threads on the other end of the new gas pipe, and screw on a coupling by hand. Tighten the coupling to the pipe with the wrench. Continue installing the gas pipe sections and couplings to create the new gas line route. Note that different-angled couplings are available to create the required bends in the new gas line route.
Wrap yellow sealing tape clockwise around the threads on the end of the last section of gas pipe. Screw a gas shutoff valve onto the pipe end by hand. Tighten the valve to the pipe with the pipe wrench.
Turn on the gas supply at the gas meter. Turn on the newly-installed gas shutoff valve for 5 seconds to remove all air from the new gas line. Turn off the valve.
Mix together some soap and water to make a milky solution. Brush the solution around all newly-installed coupling joints, as well as where the shutoff valve attaches to the end of the gas pipe. Wait for the solution to settle, and then look for any bubbles. If any bubbles are seen, gas is escaping from the coupling fittings/shutoff valve, and the new pipes must be tightened to the couplings/valve until the bubbles cease.
If the old gas pipes, couplings and shutoff valve are in good shape, they can be used in the new gas line route. Gas couplings come in straight, 30, 45, 60 and 90-degree angles, as do T-couplings for joining one pipeline to another.
Call a city inspector to inspect the new gas line route to ensure it is not leaking.