Slipline adjustable manhole seal

DETAILED DESCRIPTION What is claimed is: 1.
The method of retrofitting an in-ground drainage system with a drain pipe liner comprising the steps of: providing an elongated access opening in an existing drain pipe; providing a flexible sleeve-like gasket; sealing a circumferential end portion of the outer surface of said flexible sleeve-like gasket to the drain pipe inner surface to provide a first seal; feeding a flexible liner into the access opening along the drain pipe and through said gasket until the liner lead end reaches a drain pipe accessible end; and sealing a circumferential end portion of the inner surface of said flexible sleeve-like gasket to the flexible liner outer surface near the lead end thereof and adjacent said drain pipe accessible end to provide a second seal, said first and second seals being separated somewhat along the common axis of elongation of the drain pipe and liner, whereby a body portion of said sleeve-like gasket between said seals is free to flex to accommodate any expansion and contraction of said liner.
2.
The method of claim 1 wherein the second seal is achieved by constricting a sleeve-like gasket about the liner.
3.
The method of claim 2 wherein the first seal is achieved by radially expanding the sleeve-like gasket within the drain pipe.
4.
The method of claim 1 wherein the drainage system is of the type having a plurality of spaced apart manholes providing access to drain pipe ends, the sealing steps being performed from within a manhole.
5.
The method of claim 4 wherein the step of feeding includes passing the liner lead end beyond the drain pipe accessible end sufficiently far to allow the liner trailing end to enter the drain pipe through the access opening whereupon the liner is fed in an opposite sense until the trailing end reaches a drain pipe end in another manhole.
6.
The method of claim 5 including the additional step of sealing the flexible liner outer surface near the trailing end to the inner surface of the drain pipe.
7.
The method of claim 1 including the preliminary step of inserting an annular centering ring into the drain pipe accessible end, the annular centering ring having an outside diameter near the inside diameter of the drain pipe and an inside diameter near the outside diameter of the liner