How can I avoid a gas line when hanging shelves?

Question

I am planning to build shelves next to my water heater. I am planning to make shelves easily removable so it would be possible to service and replace heater without any problems. Here is how it is located:

It seems like I need to leave about 3 inch clearance for air flow and to avoid any fire hazard. My question is about location of gas line. I am planning to attach 2x4 to the wall indicated in the following picture:

As you can see there is gas line running in this wall. I will exercise caution and when predrilling holes will try to stay away from the gas line and will listen how drill bit moves, but in general how can I make sure that I do not hit a gas line in my house either in this project or any other where I have to make holes in the walls?

Answer 1

Regarding clearances: every gas-burning appliance has specific clearances required to combustible materials. These should be printed on a label right on the appliance. Your water heater has this information on the label at the upper-left of the large area of labels but the photo isn't quite clear enough for me to read what the clearances are. Don't just guess what the clearances should be.

Your gas line is black pipe, which is a kind of steel pipe. Plumbers don't like making their lives hard so we can be reasonably confident the gas line doesn't go horizontal and doesn't go down into the concrete floor. It most likely goes straight up - so don't drill within an inch or two to either side of that line.

Black pipe is fairly tough stuff. If you're running a drill bit into wood and run into black pipe you will (should!) notice the drill stopped advancing well before any real harm is done. If one were driving a screw into wood and happened to collide with black pipe that crossed through that wood I'm not sure what would happen -- but I think it's most likely that the screw would snap off rather than pierce black pipe. In a contest against copper or plastic pipe, though, the screw would likely win.