California Uniform Plumbing Code
Summary of Requirements For Gravity Systems*
For general requirements and good practices see the FAQ page for Gravity System Requirements:
- Minimum disposal field: 150 sf
- Maximum drain line length: 100'
- Minimum depth of cover: 12"
- Tench width: 18" min. to 36" max.
- Trench depth, below leach line: 12" min. to 36" max.
- Sidewall beyond minimum can be counted in absorption area.
- Maximum drain line grade: 3" in 100'
- Minimum gravel: 2" over drain line and 12" under
- Minimum separation to ground water: 5'
- Minimum center-to-center drain line spacing: 6'
- Minimum spacing between trenches: 4' + (2' for each foot of depth beyond minimum)
- Distribution boxes shall be set on a level concrete slab.
- Leachfields greater than 500 lf require a pump (2 pumps at 1000 lf).
- Bed style disposal field: areas must be increased by at least 50%; drain lines maximum 6' center-to-center.
UPC Setback Requirements
For a graphical representation of the UPC setback requirements:
*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 the state's official website:
Link to State UPC Website
For a pdf of the UPC: