In the past I have written a number of articles about underground fuel tanks, both heating oil and gasoline tanks. Such tanks were common in older homes and, sometimes, I find homes where the tanks are still in use supplying a furnace. The most common signs of a storage tank underground consist of seeing either the vent, or breather, pipe. Or a fill pipe or cap. The first photo is a vent at an underground oil tank. The next one is the fill tube and cap for an old underground gasoline tank. Another thing the inspector might see is a small diameter copper pipe entering a basement or a crawl space wall. Since I have written about this topic before, my intent here is to show a schematic view of what these systems look like if one can only get under the soil. I have had clients who are confused by the configuration. They cannot visualize how the system is setup. I think the photo below makes it all pretty clear. That is the fill pipe at the right and the vent at the left. You can also see a fuel line entering the home. Thanks for stopping by, Steven L. Smith