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A California C-42 Sanitation System contractor license lets you fabricate and install septic tanks, storm drains, and other sewage-disposal structures for hire. It requires passing CSLB’s C-42 trade exam and the Law & Business exam, plus at least four years of qualifying sanitation-system experience.
What does a C-42 license cover?
A sanitation system contractor fabricates and installs cesspools, septic tanks, storm drains, and other sewage disposal and drain structures, including laying cast-iron, steel, concrete, and vitreous or nonvitreous pipe and associated hardware. (Source: California Code of Regulations, Title 16, Section 832.42.)
How do I get a C-42 license?
You’ll need at least four years of qualifying sanitation-system experience within the last 10 years, a completed CSLB application, and passing scores on both the C-42 trade exam and the Law & Business exam. See our step-by-step application guide and current fee and bond breakdown.
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Facts on this page are checked against the California CSLB C-42 classification description (CCR Title 16 §832.42).
Last updated: July 16, 2026. Accuracy method: every code citation and answer is verified against current code editions and licensing-board requirements, and corrected as codes change. Refund policy.
C-42 Sanitation System exam — frequently asked questions
What does a C-42 Sanitation System contractor license cover?
A C-42 contractor fabricates and installs cesspools, septic tanks, storm drains, and other sewage disposal and drain structures, including laying cast-iron, steel, concrete, and vitreous or nonvitreous pipe and associated hardware. (Source: 16 CCR Section 832.42.)
Does C-42 include septic tank installation?
Yes — septic tank fabrication and installation is explicitly within the C-42 scope. (Source: 16 CCR Section 832.42.)
Does C-42 cover storm drains?
Yes — storm drains and other sewage disposal and drain structures are included. (Source: 16 CCR Section 832.42.)
What score do I need to pass?
The C-42 trade exam is 115 questions in 3.5 hours, closed-book, at a PSI test center, with a 73% passing score. (Source: CSLB Examination FAQ.)