Sorry my reply is so late, was having problems with my keyboard. Anyway I don't want to tell you a depth without knowing your local code. However here's a piece of advice. If you have natural gas service coming into your house from the main, remove the cover for the shut-off valve on the sidewalk or lawn and stick a tape measure down the hole until it hits the valve. There's your depth. I'm sure your local gas supplier will also tell you how deep you need to go. Good Luck.