Plumbing Contractor (C-36)

California Plumbing Contractor License (C-36)

The California Contractors State License Board (CSLB) issues the C-36 Plumbing Contractor license. CSLB's classification page says C-36 covers plumbing systems that transmit gases or liquids, including water supply, drainage, waste, vent piping, gas piping, fixtures, and appurtenances that form part of a plumbing installation.

When a CSLB license is required

CSLB says a California contractor license is generally required when:

• the project requires a building permit
• the work uses employee labor
• the combined labor-and-material cost is $1,000 or more

Requirements

• Experience: CSLB generally requires at least 4 years of journey-level or equivalent plumbing experience within the last 10 years for the qualifying individual
• Examinations: Applicants must pass the Law and Business exam and the C-36 trade exam unless CSLB grants a waiver
• Bond: An active contractor license bond of $25,000 is required before CSLB will issue the license
• Fingerprints: Live Scan fingerprinting is part of the application process
• Workers' compensation: CSLB requires a Certificate of Workers' Compensation Insurance or a valid exemption filing before license issuance, depending on whether the business has employees
• Asbestos open-book exam: After passing the license exams, applicants must submit the asbestos open-book exam verification form before CSLB will process the license issuance

Renewal Information

• Renewal Period: Active licenses expire every 2 years
• Timely Active Renewal Fee: $450 for sole owners or $700 for non-sole owners
• Late Renewal Penalty: $225 for sole owners or $350 for non-sole owners, reflected in CSLB's current delinquent active totals
• Delinquent Active Renewal Fee: $675 for sole owners or $1,050 for non-sole owners if CSLB receives the renewal after expiration
• Retroactive reinstatement window: CSLB's current renewal guidance says a completed renewal received within 90 days of expiration may qualify for retroactive reinstatement under the statute
• Continuing education: CSLB does not publish a general continuing-education requirement for C-36 license renewals

Scope of Work

CSLB's C-36 classification covers water supply, drainage, waste and vent piping, gas piping and appliances, solar water heating, compressed air, medical and industrial gas piping, vacuum systems, water conditioning equipment, backflow preventers, gas earthquake valves, and on-site disposal systems that form part of a plumbing installation.

Compliance Risk

California treats unlicensed contracting as a serious enforcement issue. CSLB says first-time unlicensed contracting offenses are usually misdemeanors that can bring up to six months in jail, a $5,000 criminal fine, and an administrative fine of $1,500 to $15,000 (effective July 1, 2026; prior to July 1, 2026: $200 minimum). C-36 contractors also have to keep the right workers' compensation filing on record with CSLB before the license can be issued or maintained in active status.

How to get a C-36 classification

CSLB's C-36 classification is scoped tightly to plumbing systems inside a structure, not everything on a job site that moves water or heat.

Scope, and where it stops. C-36 covers water supply piping, drain-waste-vent systems, gas piping and appliances, and water-heating equipment, plus the backflow preventers, water-conditioning equipment, and gas earthquake valves connected to those systems (16 CCR §832.36). It stops at the building's boiler and steam systems — that is C-4 (Boiler, Hot-Water Heating and Steam Fitting) work. It stops at warm-air heating, ventilating, and air conditioning — that is C-20. And it stops at underground sanitation infrastructure outside the structure: septic tanks, storm drains, and sewage disposal structures fall under C-42 (Sanitation System). A plumbing contractor who also services a boiler or lays a septic line is working outside C-36 and needs the matching classification to do that part of the job legally.

Experience and exams. The qualifying individual needs 4 years of journey-level plumbing experience within the last 10 years, verified by a certifier with direct, firsthand knowledge of the work — not a secondhand or supervisory-in-name-only sign-off. Up to 3 of those years can come from qualifying education, but at least 1 year has to be hands-on. Once the application is accepted, the qualifier sits for two exams: Law and Business and the C-36 trade exam.

Fees.

The $25,000 bond has to be in place before CSLB issues the license.

Workers' compensation. C-36 is not one of the classifications CSLB bars from the no-employees exemption — that list is C-8, C-20, C-22, C-39, and C-61/D-49 under Business and Professions Code §7125. A solo C-36 contractor with no employees can file the exemption and skip workers' comp coverage. But the exemption is a sworn statement, not a formality: filing it while employing someone subject to workers' comp law, or continuing to claim it after hiring, is cause for disciplinary action under §7125. The moment a C-36 contractor hires anyone, the exemption on file stops being valid, and a Certificate of Workers' Compensation Insurance has to replace it within CSLB's filing window — not indefinitely.

Renewing a C-36 license

The renewal fees and late penalties above are the current numbers — for the full renewal process, deadlines, and reinstatement window, see the California contractor license renewal guide. A C-36 contractor who added employees since the last renewal needs proof of coverage on file before CSLB will process the renewal.

*Disclaimer: This information is provided for general reference only and does not constitute legal advice. Always verify current requirements directly with CSLB before applying, bidding, or renewing.*