Spills and Backwater Valves

Most properties are connected to public (mainline) sewers. The majority of these properties have been built so that an obstruction in the public sewer will not cause sewage backup into the property.

Other properties, however, require the protection of a backwater valve in the owner's drain line. These properties have been built (see diagram) so that the drain of the lowest plumbing fixture (bath tub, shower, etc.) is lower than the upper manhole (maintenance hole) of the public sewer. The backwater valve is designed to automatically shut to prevent sewage from backing up into the building from an obstructed public sewer.

If your property appears to require a backwater valve, but you do not know if one has been installed, we strongly encourage you to call a licensed plumber, who can evaluate your situation and, if necessary, install a backwater valve. Backwater valves must be checked to ensure that they are operating properly at all times. Root cleaning machines, debris in the drain line or other problems can easily damage or interfere with the proper operation of backwater valves.

A plumbing permit is required for the installation of a backwater valve. See http://www.ladbs.org/ to get more information.


spills and backwater valves
red pipes of pumping station

The most common causes of spills in homes and businesses are fats/oils/grease (FOG) and tree roots. The result can be a sewage overflow, usually through maintenance holes and onto the street. The sewage then runs into the gutters and eventually into storm drain inlets. The storm drain system is connected to our rivers, the Santa Monica Bay, and the ocean. Spills create a hazard that is potentially dangerous to our health and the environment because the wastewater that overflows is not treated.

Sewage blockages can also cause backups into homes and businesses that do not have properly operating sewer backwater valves.

LA Sanitation maintenance crews proactively maintain sewer lines and pumping plants to prevent spills. They also respond to emergencies when a sewer blockage occurs. The number of spills in the City has significantly decreased over the last five years as a result of these efforts.


  • Sewer odor complaints reduced by 52% since FY 2009
  • Spills reduced by 82% over past twelve years