Smaller HDPE gas mains such as 8, 6, and 4" are typically buried about 3 ot 4 feet deep; however proper locating officials MUST be called and notified and locates made accurately BEFORE any digging takes place for other purposes, such as water lines, poles, and fences. Talk to the utility owner that installed the gas line for the exact depth as it is critical to safety.
Different geography demands different depth. Avoiding the frost line is important to avoid movement of the pipeline during freeze and thaw cycles. Pipe movement can pull apart fittings and place stress on elbows and other angles.
It's best to call Diggers Hotline (free) so they can mark the location of the various underground utility lines. They'll mark the locations (but not the depth). The depth of utility lines varies, but could be 18 inches. Natural gas lines are usually plastic and at higher pressure than at your home appliance (regulated by the gas meter).
500mm
They are called gas lines.
Brass fittings can be used underground for water lines; always check your local code office first. They should not be used for gas lines.
A spirit raised from depth of underground.
underground gas lines used to be wrapped i tape because soil corrodes metal pipe. Now most gas lines are run in a poly pipe or pipe that has a coating applied from the manufacturer to prevent the corrosion
underground
You open the gas cap and this will depressurize the gas lines.
Yes, there are certain zoning codes for different areas. There are also gas and water lines underground that you should be aware of. There should be a number you can call to find out exactly where those lines are and how to get a permit for the addition.
Most main lines are at least 24 inches before final grade. Drops catv/phone 4-10 in. But be sure to call in to your local one-call service to have them marked.
fathoms
none, but there were some underground gas chambers