Customer-Owned Buried Pipes
Gas companies own and maintain pipes that run to your gas meter. But it's up to you to maintain pipes from the meter to your gas-burning appliances. Don't know if you have buried piping? If you have a gas grill, heater in a detached garage, a gas-heated pool, or any gas-operated appliance away from your house, you probably have piping that you need to care for. That also includes a line that runs from the meter and underground before it reaches a basement.
If it sounds like you have buried piping, contact a qualified professional periodically to check the pipes for corrosion or leaks. It's also a good idea to document where those lines are, and keep that documentation in a safe place - like a safety deposit box. You never know when you might need it, or if someone who wants to purchase your home would like to know the locations.
Some companies recommend black iron pipe or corrugated stainless steel tubing for natural gas piping within your home. If the pipes are buried, they should be coated and cathodically protected. For details on specific local requirements for pipes, contact your city or county government.
You should also check up on the fittings and connections of your pipes to ensure they are in good working order.

