Abstract: A sleeve covering to surround a vent pipe which is to be buried and inserted into and connected to a T-fitting trap of a sanitary sewer system is described which sleeve covering will prevent the frost or frozen earth from heaving the pipe which it surrounds. The repeating sleeve covering is basically a number of hollow vertical sections or coupling members, generally cylindrical in shape, whose inside diameter of the bottom portion of each is slightly greater than the pipe which it surrounds. Vertical movement of the sleeve sections or coupling members (one or more or all) is possible without causing any vertical movement of the pipe that the sections surround. Also, because of the particular exterior shape (frusto-conical) of the top portion of each section, the exterior forces exerted upon same by the earth when it freezes actually tends to force the sleeve sections downward rather than upward.

Abstract: A method of and an apparatus for relieving ground pressure surrounding pvc vent pipes which have been displaced from their T-fitting traps in sewer systems. The round tubular nature of a semi-rigid pipe is changed to an elliptical or oval shape with initial insertion and rotation of a special tool. The tool being connected to a drive-shaft and rotated by an external source such as a drill motor. The rotation of the tool within the pipe progressively causes the pvc pipe to have a momentary elliptical cross-sectional shape as the tool rotates within the previously round pipe, without rotating the pipe. As the tool passes down (or "screws down") through the pipe, the pipe re-assumes its circular cross-sectional shape, and original diameter, but only after its larger-dimension elliptical cross-section has pressurized the earth duct and increased its diameter to about an inch greater than its initial (unpressured) circular diameter.