Causes of sewer failure:
Broken, cracked, missing, or off set pipes – Early materials for constructing sewer lines were made of brittle, vitreous material. Over time these materials have worn down and become defective. Colder climates also put undue pressure on these systems as the ground continuously shifts from season to season.
Blockages – A sewer line can only handle so much debris before it will become plugged. The number one cause of blockage is tree roots. Tree roots are able to enter the line by any number of deformities, but mainly shifted joints are the culprit. Once tree roots enter the line, any grease, hair, food particles from garbage disposals, etc., will slowly begin to build up until flow is completely restricted.
Corrosion – Any sort of metal pipe that has been subject to chemical treatment such as paint thinners, or liquid drain cleaners, has the possibility of corrosion from the inside out. Horizontal pipes don’t require much grade, so over time these chemicals may sit in one place and slowly corrode the pipe.
Bellied or Disconnected Pipe – The original installation may have not been performed correctly. This could have caused a pipe belly or separation that would allow build up in the belly or a plug to form in the line.