C-42 Sanitation System Contractor license in California

Updated November 1, 2026 · Official name from CSLB's classification list

• 978licenses hold C-42
• 97.4%Clear (CA addresses)
• 35%workers' comp exempt (all: 49.6%)
• 99.9%contractor's bond on file
• 20.6 yrsmedian time licensed
• 64.6%businesses, not sole owners

Sanitation system contractors fabricate and install cesspools, septic tanks, storm drains and other sewage disposal and drain structures. Laying cast-iron, steel, concrete and plastic pipe for these systems is part of the class.

In rural and hillside areas without a sewer, a C-42 is often the specialist for a new septic system or a failed leach field. Plumbers can also do on-site waste systems, so you may see either license on a septic job.

Typical work under C-42

• Septic tank installation and replacement
• Leach field and drain field work
• Storm drains
• Sewer laterals and drain structures
• Abandoning an old cesspool

Work that needs a different license

• Drain and vent piping inside the house: C-36 Plumbing
• Large public sewer mains: A General Engineering or C-34 Pipeline
• Grading the yard after the work: C-12 Earthwork and Paving

Tips before hiring

• Ask whether a percolation test or soil report is needed and who orders it.
• Ask where the tank and field will sit relative to wells, property lines and future building spots.
• Get a pumping and inspection schedule for the new system.
• Ask whether the county environmental health office must approve the design before work begins.

Where C-42 contractors are

The cities with the most C-42 license holders in CSLB's current file:

1. Septic and Sanitation Contractors in Oakland: 28
2. Septic and Sanitation Contractors in San Jose: 20
3. Riverside: 17
4. Sacramento: 14
5. Los Angeles: 13
6. Santa Rosa: 12
7. Bakersfield: 11
8. Hayward: 11
9. Chico: 10
10. Sylmar: 10

All septic and sanitation contractors lists

Cities with at least 20 C-42 license holders, largest first:

• Oakland (28)
• San Jose (20)

How to verify a C-42 license

1. Search the business or license number here and confirm C-42 is listed on the profile.
2. Check the same number on CSLB's Instant License Check.
3. Read our full guide to checking a contractor license.

Related license types

• C-36 Plumbing Contractor
• C-34 Pipeline Contractor
• C-12 Earthwork and Paving Contractors
• C-57 Well Drilling Contractor

Source: CSLB public data · Updated November 1, 2026 Status can change at any time. Verify on CSLB's Instant License Check.

More license types: ← C-39 Roofing Contractor · C-43 Sheet Metal Contractor →