Shut off the main gas line at the house. Turn the lever on a natural gas line so it is at a right-angle to the pipe. For propane gas, twist the knob on the main valve clockwise until tight.
Fasten the connector on the end of the house line to the free end of the hose attached to your gas grill. Twist the threaded connector for a propane line clockwise until tight. Natural gas lines use a bayonet-style connector that inserts into the coupler on the grill and twists 1/4 turn clockwise to lock.
Pour liquid soap and water a spray bottle. Shake to create suds.
Open the main gas valve for the house line to release gas to the grill.
Squirt soapy water on the connection between the house line and grill to check for leaks. If you smell rotten eggs or notice rapid bubbling in the soap suds, you have a leak. Shut off the gas line and repeat the connection.