Civil-Environmental Engineering
Lassen County

Cities and towns (requirements may differ)​

*The information on this page is a summary for quick reference only and may not represent the latest standards.  For complete and up-to-date information, see each counties official website.

Summary of Requirements For Gravity Systems*

Lassen County uses the California Uniform Plumbing Code with the following modifications:


  • Trench Sidewall-to-Sidewall Separation: 4'

  • Minimum Spacing Between Lines: 6 ft

  • Minimum Total Trench Length: 100 ft

  • Maximum Trench Length each: 100 ft

  • Bottom Width: 18" to 36"

  • Trench Depth: 3 ft minimum

  • ​Minimum of 2" of gravel over drain lateral, and 12" under.

  • Drain Line and Trench Bottom must be level.

  • All Drain Lines should be of equal length.

  • Drain rock should be 1 1/2" to 3", covered with straw, untreated building paper or filter fabric.



For general requirements and good practices see the FAQ page for Gravity System Requirements:


For UPC specifics: ​

For Lassen County Individual Sewage Disposal System Handout 2005 version (copy obtained July 2013) - includes setback table and diagram: ​

For Lassen County Chapter 12 Septic Regulations (copy obtained July 2005): ​



Links to Lassen County Website

For County home page:

For County Building Code: