Sewage flows by gravity though a system of underground pipes. When the flow is obstructed the sewer may back-up into the property owner's building. There are three types of sewer back-ups: private service line blockage, city main blockage and catastrophic situations. Most sewer back-ups are preventable.
Service Line Blockage
In service line blockage only one property is affected. These include back-ups related to tree roots and any thing that will not totally dissolve that could plug the sewer service such as disposable diapers, sanitary napkins, bandages, rags, and plastics bags. The property owner is responsible for the repairs and maintenance of the sewer service from the City sewer main.
Sewer Main Blockage
A sewer main blockage will most likely affect more than one property. Sewer mains may back-up when the sewer main pipe breaks down. The City routinely inspects the sanitary sewer system to prevent sewer main failures. Sewer main back-ups may also be caused by the same items that cause private service line to back up. These items manage to flow through the private service line but then get stuck in the main. Improper cleaning of a private sewer services may move the blockage problem further down stream into the sewer main. Construction activates from time to time accidentally create blockage problems as well.
In catastrophic situations large numbers of properties are likely to be affected. These include back-ups related to exceptionally heavy rainfall exceeding the "100-year" amount; back-ups due to flooding; back-ups due to an extended power outage; and any disaster type situation. Federal Emergency Management Administration (FEMA) usually provides funds to assist property owners in catastrophic situations.