Typical Sanitary Sewer System Problems
Causes of Sewer Backups
Infiltration/Inflow Correction Program (I/I Program)
Methods to Determine the Condition of the Sanitary Sewer System 


  • Old and deteriorated main and lateral pipes - Sewers range in age from 30 to 100 years with an average age of 50 years.
  • Cracked sewer pipes - Existing sewers are mostly clay pipes which can crack as they deteriorate with age and also by earth movement.
  • Misaligned and open pipe joints - Most of the mortar used to seal the joints between sections of clay pipe has deteriorated.
  • Undersized sewer pipe - The existing sewer system is overloaded due to new sewer hook-ups, underground water infiltration, and illegal roof and/or yard drain connections.
  • Defective manholes - Old manholes are made of bricks. Typical problems associated with brick manholes are loose bricks, missing bricks, and misaligned manholes.
  • Missing and/or unrecorded sewer pipes and manholes - This problem is typical in the easement/backline sewer. Sewer pipe locations shown on the sewer record map are different from the actual sewer location.
  • Sewer main under houses and other improvements - Complaints of sewer main alignment crossing the house and other improvements. A solution to this problem requires an agreement with the property owner for a new sewer easement at a relocated line.
  • Flat or level sewer main/lateral - Located mostly in flat areas of Berkeley (South Berkeley, West Berkeley, and Oceanview). Requires sewer replacement to bigger size and redesigned pipe slope.

Image of typical sanitary sewer problems

Image of typical house connection to sanitary sewer system



Sanitary sewer backups are caused by several factors including the condition of the sanitary sewer system itself, natural phenomena such as earth movement and rain, and the incorrect usage of the system by the public.

Examples of backup causes are:

  • Root infiltration - Tree roots are a major cause of backups.
  • Water inflow/infiltration - Rain water entering the sewer pipe causes overflows.
  • Solids - Typical solids that buildup in the pipe and cause backups are grease, dirt, bones, tampons, paper towels, diapers, broken dishware, garbage, concrete, and debris.
  • Structural defects in pipes and manholes - Sags in the line, cracks, holes, protruding laterals, misaligned pipe, offset joints are all possible causes of backups.


Infiltration/Inflow Correction Program (I/I Program)  

  • Cease and Desist Order Sewer Rehabilitation Program - This program is part of the City's mandated sanitary sewer correction program under the Regional Water Quality Control Board (RWQCB) and Environmental Protection Agency (EPA) Cease and Desist Order Compliance Plan to reduce storm water infiltration and inflow into the sanitary sewer system.
  • Cyclic Sewer Rehabilitation Program - This rehabilitation program is to correct I/I sources identified through field works and various complaints by the public and City maintenance work order records. This is localized sewer rehabilitation work that requires immediate attention to protect the public from continuous exposure to raw sewage.
  • Trunk/Relief Sewers - These are larger diameter sewer pipes, size ranging from 12" to 36" diameter, which convey sewage from various collector sewer pipes to EBMUD sewer interceptors. Relief sewers are constructed to eliminate sewer overflows due to inadequate capacity on existing trunk sewer pipes. Major relief sewer mains were constructed during the first 5 years of the I/I Sewer Program.
  • Emergency Sewer Rehabilitation Program - These are sewer rehabilitation projects that require immediate attention to eliminate known health and safety hazards. Typical problems on these high priority projects are continuous sewage overflow onto private properties and creeks and collapse of the street pavement due to underground cavities caused by leaking sewer pipes.
  • Proactive Backline Sewer Program - Approximately 27 miles of the City's sewer system are located in easements on private property in hilly areas in the northern and eastern sections of the City and in the Claremont areas near Tunnel Road. Backline sewer mains are difficult to access and maintain. They are frequently in areas covered by vegetation, trees, landscaping, and building improvements.


Methods to Determine the Condition of the Sanitary Sewer System  

  • Physical inspection - This involves examining the physical condition of manholes and other sewer structures to determine their structural integrity and to identify possible sources of infiltration/inflow (I/I).
  • Flow monitoring/flow isolation - Rainfall gauges are installed to monitor subbasins with overflow problems by collecting and analyzing flow data during normal and storm related weather events.
  • Smoke testing - Smoke testing is used to locate specific defects (leaks) in sewer mains and laterals that contribute infiltration/inflow to the sewer system. Smoke testing involves injecting a non-toxic vapor (smoke) into the manholes and following its path of travel in the mains and laterals.
  • Dye water flooding - Colored dye is added to the storm drain water. Dyed water appearing in the sanitary sewer system indicates an existing connection between the sewer and storm drain system.
  • Closed-circuit television inspection - This is a useful tool in locating specific sources of infiltration as well as determining the structural condition of the sewer system. This information is necessary for the design of sewer replacement and rehabilitation projects.
  • Sewer maintenance records - Records of frequent maintenance problems.