Sewer renewal methods
In general, there are three ways to renew a sewer connection: open trenching, pipe bursting, and pipe relining.
With open trenching, City crew dig a trench, locate the sewer lines, and then repair or replace the pipes.
Roads, sidewalks, yards, driveways, and landscaping may be disturbed when locating and repairing sewer pipes. As well, sewer services can sometimes run directly underneath other utilities and large trees with extensive and sensitive root systems. In these situations, repairs can be difficult and expensive because they require hand digging around the other utility lines or roots.
With pipe bursting, City crew use existing pipes to lay in new sewer lines.
Pipe bursting is a newer method and has replaced open trenching as the method of choice to renew selected sewer lines and main lines. Pipe bursting takes relatively little time, but depends on specific conditions in order to be effective:
- The old pipe must be relatively straight
- The existing line must be free of dips, bends, and blockages
- There must be sufficient area on the private property to dig a launch pit in order to feed the new pipe.
To start the pipe bursting method, the City crew digs a launch pit at one end of the failed sewer pipe, usually near the home. They then dig an exit pit at the other end, usually near the sewer main. A pulling cable is fed through the old sewer connection. Attached to the pulling cable is a steel bursting head positioned on the old pipe at the launch pit.
At the exit pit, a hydraulic puller maintains constant tension on the bursting tool as it pushes through the existing sewer connection. The bursting tool follows the existing sewer connection to guide the new pipe into place.
With pipe relining, City crew repair existing sewer lines temporarily.
Pipe lining is a practical method when the pipe bursting method cannot be used, or when a two line sewer connection is not available on the public side. It requires minimal excavation. However, relined pipes are about half as durable as completely replaced pipes.
Pipe relining fills cracks by inserting a long cloth sleeve treated with epoxy resins into the existing pipe. The sleeve is molded to the inner wall of the existing pipe with compressed air. The new liner adheres to the wall of the pipe and after several hours, the liner is ready to stand alone. The effect is a pipe within a pipe. Over time, relined pipes need to be replaced using one of the other methods - open trenching or pipe bursting.