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How to Take Care of Your Sewer Lateral

Sewer lateral diagram

We often receive questions from property owners about their sewer laterals and whose responsibility it is to identify and solve problems with them. The sewer lateral connects the plumbing fixtures of a building (toilets, sinks, showers) to the sewer main, which runs underneath the street all the way to a wastewater treatment plant. While the sewer main belongs to the San Francisco Public Utilities Commission (SFPUC), the entire sewer lateral belongs to the property owner and is the property owner’s responsibility to maintain. The property owner must hire a licensed plumber or contractor to proactively inspect and maintain the entire lateral, and to repair or replace the upper section of the lateral if needed. Under most circumstances, the SFPUC will repair or replace the lower section of the lateral.

Understanding the Upper and Lower Lateral

A sewer lateral is one pipe that consists of two segments: the upper lateral (sometimes called “building sewer” or “building drain”), which runs from the building to the curb; and the lower lateral, which runs from the curb to the sewer main (usually located in the street). The upper lateral also includes a sewer vent (sometimes called “fresh air inlet”) that runs vertically to the sidewalk, and a trap (sometimes called “building trap”), located at the bottom of the vent. The property owner owns the entire sewer lateral, including the upper lateral, lower lateral, vent and trap.

How to Maintain Your Sewer Lateral

As the property owner, you are responsible for maintaining and inspecting your entire sewer lateral (both upper and lower) to ensure it is in good working order. This responsibility includes, but is not limited to, the following:

  • You should keep your lateral in good condition by not flushing anything down the toilet except poop, pee, and toilet paper, and by not pouring fats, oils, and grease down the drain.
  • If you experience an issue with your lateral, such as sewage backing up within your property (bathroom or kitchen fixtures, basement, garage), you should hire a licensed plumber or contractor to inspect the lateral. It may just need to have debris cleared out from the pipes, or it may be a more serious issue that requires you to repair or replace some or all of the lateral (see below).
  • Even if you are not currently experiencing issues, you should hire a licensed plumber or contractor to proactively inspect your lateral at least once every five years.

Property Owners Must Repair or Replace the Upper Lateral

It is your responsibility to repair or replace your upper lateral if your plumber or contractor’s inspection identifies a problem that cannot be fixed with maintenance. You must hire a licensed contractor or plumber to remedy the problem and repair or replace any damaged portion of the upper lateral (including the vent and trap) as needed. Contact the Department of Building Inspection to verify whether you need a permit: (415) 558-6570 or

Repair or Replacement of the Lower Lateral

If your plumber or contractor’s inspection identifies a problem with your lower lateral that cannot be fixed with maintenance, you should submit a service request by calling 3-1-1 or online at This will alert the SFPUC’s Sewer Operations team, which will dispatch a crew to inspect your lower lateral. If the SFPUC inspection determines that lower lateral repair or replacement work is necessary, under most circumstances, the SFPUC will complete this work at no extra cost to you.

In Summary

Follow these steps to take care of your sewer lateral:

  1. Hire a licensed plumber or contractor to proactively inspect and regularly maintain your lateral to prevent issues.
  2. If you experience an issue, hire a licensed plumber or contractor to inspect your lateral, locate the problem, and conduct maintenance, repair, or replacement of the upper lateral if needed.
  3. If your plumber or contractor’s inspection locates a problem that may require repair or replacement of the lower lateral, contact 3-1-1 to have the SFPUC inspect it and determine next steps.

More information on sewer laterals can be found at You can also contact the SFPUC Sewer Laterals team at