To install a residential gas line, turn off the house's gas using the valve next to the gas meter, and then extend the existing gas line to the new appliance using black pipe, valves and couplings. Connect the line to the appliance using a flexible pipe, and check every seam in the pipeline using soapy water.
Black pipe for gas lines is available at hardware stores. Be sure to plot the pipe's course, and take note of any bends that require couplings. The store can cut the necessary lengths of pipe and add threading.
Begin installing the pipeline at the gas supply end, working towards the appliance. Use pipe glue or tape to secure every coupling and valve; the connection should be airtight. Be careful not to tighten the pipes too much, as this can damage the threads. Tighten the pipe by hand, and then tighten it slightly more using a wrench. Install a shutoff valve close to the appliance, and remember to secure the pipe to studs and floor joists where possible.
Once the pipe is in place, pour a mixture of water and dish soap over every new joint. If bubbles appear, there is a leak in the line, and the section of pipe must be reinstalled with fresh pipe glue. To be completely sure the line is safe, have an inspector check the pressure in the line.
After sealing any leaks, turn the gas on, and make sure the appliance is working properly.