Service line interior by-pass

A method of installing an interior by-pass liner tube within a conduit comprising the steps of attaching a substantially cylindrical adapter to, and forming a continuation of, each end of said liner tube, each said adapter having a longitudinally spaced-apart pair of peripherally extending an exteriorly mounted radially expandable sealing gaskets thereon, inserting said liner tube within said conduit and, when each of said liner tube end adapters is in its intended position within said conduit, expanding said gasket pair on each adapter radially into sealing engagement with the surrounding interior surfaces of said conduit while providing a gas leakage passage having an interior end terminus within said cylindrical adapter and an exterior end terminus on the exterior of said adapter within the region between said pair of gaskets thereon, whereby said interior by-pass liner tube is installed substantially permanently within said conduit by said sealing engagement of said gasket pairs at each of its ends with said conduit interior surfaces, and the interior of said liner tube has gas leakage communication with the respective interior surface portions of said conduit and the peripheries of said gaskets between each of said gasket pairs, and simultaneously testing the gas-tight effectiveness of said liner tube and said pairs of sealing gaskets at both ends thereof after said installation comprising applying test gas at a known pressure into said liner tube from the open end of said adapter at one end of the liner tube while providing a temporary seal against loss of said test gas pressure at a location substantially adjacent to the other end of said liner tube and whereby said test gas pressure is applied to said interior end terminus of each of said gas leakage passages, and observing said applied gas pressure for a period of time sufficient to determine whether any variation occurs in said known test gas pressure.