For most plumbing work in Sonoma County you need a contractor licensed by the California Contractors State License Board, and for standalone plumbing the relevant classification is C-36 Plumbing. California's minor work exemption only applies where the combined labour and materials come to under $1,000 and other conditions are met — which covers very little real plumbing. A repipe, a water heater replacement, a sewer lateral repair or gas line work all sit well outside it. The licence number itself is easy to verify, takes two minutes, and is worth doing before work starts rather than after.
How to check a licence properly
- Ask for the eight-digit CSLB licence number and the exact legal business name.
- Use CSLB's official Check a License tool at cslb.ca.gov, searching by licence number — that is the most reliable search.
- Confirm each of these: - Status is Active, not expired, suspended or revoked - Classification includes C-36 Plumbing for standalone plumbing work - The business name on the CSLB record matches the estimate and the contract - Bond information is current - Workers' compensation is listed if the company has employees - Any disciplinary history is acceptable to you
- Check again immediately before signing and before work begins. A number printed on an estimate or a vehicle is not verification.
- Make sure the written contract carries the licence number, scope, price, payment schedule, materials, warranty, and who is responsible for permits and inspections.
Use CSLB's own site rather than a third-party lookup service.
What C-36 covers, and what it does not
C-36 is plumbing. It is not a general licence, and classifications matter more than people expect.
A properly licensed B General Building contractor can perform plumbing as part of a broader building project. What you should not assume is that a general contractor's licence covers a standalone repipe — that is a scope question worth confirming with CSLB rather than taking on trust.
Equally, a C-36 does not cover HVAC (that is C-20) or solar (C-46). A plumbing contractor advertising those without the classification is advertising outside their licence.
For the record: Avanté Plumbing holds California CSLB licence #841938, classification C-36 Plumbing, held by owner Karl D'Angelo since 2004. We do not offer HVAC or solar, because we are not licensed for them.
Licensing and permits are two different things
This trips people up constantly.
A licensed contractor may still need to pull a permit for the work. They are separate requirements, and satisfying one does not satisfy the other.
In unincorporated Sonoma County, permits go through Permit Sonoma, whose published schedule lists a $327 minimum trade permit fee plus per-unit charges — $20.75 for a water heater and vent, $8.26 per water piping unit, $8.26 for a gas piping system serving one to four outlets, and a $257 plan check for a sewer line from the main to a building.
Incorporated cities — Santa Rosa, Windsor, Healdsburg, Sonoma, Cotati, Rohnert Park, Cloverdale, Sebastopol — run their own building departments. In Marin, each town runs its own.
Ask who is pulling the permit and get the answer in the contract.
Why any of this matters
An unlicensed contractor leaves you without the protections licensing exists to provide — bonding, workers' compensation cover, and a regulator to complain to. Unpermitted work surfaces at the two worst moments: when the property sells, and when an insurer asks questions after a failure.
Neither is when you want to discover the water heater was never strapped or the relief line was never run.
Related reading
Frequently asked questions
What is the minor work exemption in California? It applies where the combined labour and materials total under $1,000 and other conditions are met. Most real plumbing work exceeds it comfortably.
Do I need a C-36 specifically, or will any contractor do? For standalone plumbing, C-36 is the appropriate classification. A B General Building contractor may perform plumbing within a broader project — confirm the scope with CSLB rather than assuming.
Can a homeowner do their own plumbing? California has owner-builder provisions, and local permit application procedures vary. Confirm with the permitting agency for your jurisdiction, and note that gas and sewer work carry consequences that make DIY a poor trade.
Where do I check a licence? The CSLB's Check a License service at cslb.ca.gov, searching by licence number.