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Underground pneumatic boring/piercing tools are often referred to as hogs, air hogs or pneumatic gophers. The tool is used to bore a hole underground between two points without disturbing the surface ground. This open-air chamber is referred to as the bore hole and is used to either run ducting for product or the raw product itself between to two points.


The tool is used in the installation of all public utilities water, electricity, gas, phone, and cable television these are referred to as product. It is also used to install home sprinkler systems and auxiliary home powers lines. The tool is utilized in instances when it is difficult or cost prohibitive to plow or trench the product into the ground, some of these instances are under driveways roads, sidewalks, and landscaping. Pneumatic piercing tools are a lower cost alternative to repairing asphalt, concrete and landscaping.

How It Works

The tool uses air to pound it’s way through the ground underneath the obstruction. The tools are cylindrical in shape and range from one to eight inches in diameter and between three and six feet long. They are made from metal. Compressed air is used to power the tool; this air is run through a hydraulic hose with and oiler attachment to send oil through with the compressed air. The tool works in a way very similar to a jack hammer, and inside the cylinder is a piston. A valve opens and the air blows into the chamber forcing the piston forward which in turn propels the tool forward. The valve then shuts and the piston is pushed at a slower speed back in the tool, the valve reopens the piston pounds again and the tools moves forward.

This process is continually repeated until the bore has run the intended distance. As the tool pounds through the ground it compresses the soil. This compaction maintains the same diameter as the tool and leaves the bore hole through which the product is passed.

Performing a Bore

The purpose of the bore is to get from point A to point B under the obstruction. First the operator surveys the area and the obstacle (road, sidewalk, and driveway.) Utility locations must be present for any underground work and the path most clear of utilities is chosen to send the tool through. The first hole is now dug on one side of the obstacle. This hole must be large enough to fit the tool and the operator in it so they can aim the tool. The hole must also be deep enough that as the tool compacts the ground the surface remains undisturbed. The depth of the starting bore pit depends on the type of soil that is being worked in and how well it compacts. The operator aims the to the desired exit point and allows it to perform its function creating a bore hole under the ground without disturbing the surface. The tool is tracked by the operator who feels the tool pounding and can approximate the tools location under the ground. The operator also monitors the surface to make sure that it is undisturbed. As the tool nears the exit point it is slowed down and an exit pit is dug to locate both the tool and bore. As the tool enters the exit pit the operator chooses to either dig up the tool to retrieve it or reverses the tool back into the first bore pit to retrieve it. Now between the two pits is a completed bore under the obstacle which can be used to run the product.

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