What is a C-36 plumbing license?

A C-36 is the plumbing contractor classification issued by the California Contractors State License Board (CSLB). It authorizes a contractor to install, repair, and maintain plumbing, water, gas, and drainage systems anywhere in California. If a company is doing dedicated plumbing work in the state, this is the license they need to hold or to subcontract under.

California's licensing system uses letter-and-number classifications. C-36 is plumbing. C-20 is HVAC, C-10 is electrical, C-39 is roofing. A C-36 holder is a specialty contractor focused on plumbing, distinct from a B General Building contractor.

What a C-36 covers

The CSLB scope for a C-36 is broad within plumbing. It includes water supply piping, drain-waste-vent systems, sewer and storm drains, fixtures, water heaters and tankless units, backflow prevention devices, and gas piping for appliances and equipment. Repipes, slab leaks, sewer line replacement, and gas line work all sit under C-36.

It does not cover HVAC system installation (C-20), electrical wiring (C-10), or general building (B). A plumber running a gas line to a furnace is within scope; wiring that furnace's controls is not. On mixed jobs, contractors either carry multiple classifications or bring in a subcontractor who holds the right one.

Requirements to get a C-36

The CSLB sets a clear experience bar and two exams.

You need four years of journeyman-level, foreman, supervisory, or contractor experience in plumbing, completed within the ten years before you apply. The experience must be verifiable by someone who can attest to it, usually a current or former employer. Apprentice years do not count toward the four.

You then pass two exams: the C-36 trade exam (plumbing code, systems, materials, and methods) and the Law and Business exam that every California contractor takes regardless of trade. After passing, you submit fingerprints for a background check and post the required bonds.

What a C-36 costs

The license itself is inexpensive relative to the years of experience behind it. The CSLB application fee is about $450 and the initial license fee about $200. The $25,000 contractor bond costs roughly $100 to $400 a year, priced as a small percentage of the bond amount based on credit. Fingerprinting runs about $50. Most applicants spend $800 to $1,200 out of pocket to get licensed, before adding general liability insurance.

For the full path including apprenticeship and journeyman stages, see how to become a plumbing contractor.

C-36 vs other California plumbing credentials

People mix up the C-36 with related terms. A few distinctions matter.

The C-36 is a contractor license held by a business. It is not a journeyman card. A journeyman plumber works under a C-36 holder but cannot pull permits or contract jobs in their own name. There is also no separate state "master plumber" license in California the way there is in Texas or New York; the C-36 is the operative business credential.

A B General Building contractor is not a C-36. A B can include plumbing only on a project that spans at least two unrelated trades. For standalone plumbing, the C-36 is required.

Keeping a C-36 active

A C-36 renews every two years. The CSLB sends a renewal notice and charges about $450 for an active renewal. There is no continuing-education requirement to renew a C-36 the way some states require for plumbers, but the bond and any workers' comp coverage must stay current or the license goes to a suspended or inactive status.

A lapsed bond is the most common reason an otherwise-good C-36 shows as not in good standing. The $25,000 contractor bond protects consumers and employees, not the contractor, so it has to be renewed every year separately from the license cycle. When you verify a contractor, check the bond line, not just the license status.

How to verify a C-36 license

The CSLB runs a free public license lookup. Search by license number or business name and you get the classification (C-36), the license status (active, expired, suspended, revoked), bond status, workers' comp coverage, the responsible managing officer or employee, and any disciplinary actions. The board updates this in real time, so a contractor who renewed yesterday shows current today.

Verification matters whether you are a homeowner hiring a plumber or a vendor building a contractor list. A license number that checks out against the CSLB is the difference between a verified contractor and an unverified claim. We cover the state-by-state version of this in contractor license data by state.

How many C-36 contractors are in California

California had roughly 30,000 active C-36 licenses as of early 2026, one of the larger single-trade contractor pools in the country. The CSLB publishes the full license file on a weekly refresh, which makes California one of the cleanest states for building or validating a plumbing contractor list.

For teams that sell to plumbers, that registry is the raw material for a clean prospect list: business name, license number, status, and the responsible party, all from an authoritative source. TradeBridge builds and validates plumbing lists from CSLB and the equivalent boards in every other state. See plumbing contractor data for what a delivery includes, or license verification to check a list you already have against the issuing board.