How to Verify a Plumber License: CA, TX, and WA

Verifying a plumber license means checking two records, not one: the business that contracts for the work and the individual who performs it. In California, Texas, and Washington those records live in different databases, use different names for the same tiers, and expire on different cycles. A company can hold a valid business license while the worker on site holds the wrong credential, and a certified individual cannot legally contract for work alone. This guide walks through the lookup in each state, explains what each tier actually authorizes, and lists the checks that matter before you hire, onboard, or pay.

Last reviewed November 2, 2026. This is an operational guide, not legal advice. Confirm requirements with the state board before you sign a contract.

What are you actually verifying when you check a plumber?

Three things, in order. First, legal authority: does the business hold an active license covering plumbing contracting in that state? Second, scope: does the credential match the work, and does the individual on the job hold the matching certification? Third, financial backing: is the required bond or insurance still in force, under the same business name as your contract?

Most bad hires fail on the second item: a card, truck logo, or license number that belongs to a different tier, business, or state. The lookups below take about two minutes each and are free.

How do you verify a plumber license in California?

California licenses the plumbing business, not the individual plumber. The Contractors State License Board (CSLB) issues the C-36 Plumbing classification, which covers water supply, waste and vent systems, gas lines, and fixtures. A C-36 contractor must demonstrate four years of journey-level plumbing experience and pass a trade exam before the license is issued.

Start at the CSLB license search: cslb.ca.gov/onlineservices/checklicenseII/checklicense.aspx. Search by license number, business name, or the name of a person on the license. The license number is the most precise search, and California contractors are required to display it on bids, contracts, vehicles, and advertising.

Confirm three things on the record. The classification list must include C-36 Plumbing: a general building (B) license alone does not cover a standalone plumbing job unless the company also holds C-36 or subcontracts that work to a C-36 holder. The status must read Active, and the $25,000 contractor bond must be on file, along with workers compensation coverage if the company has employees. Read the disclosure section too: it shows disciplinary actions and citations.

California does not license individual journeyman plumbers through CSLB the way Texas and Washington do, so the business record is the whole check there, and a missing C-36 means the company cannot legally take the job as its own work.

How do you verify a plumber license in Texas?

Texas is the cleanest of the three lookups because one agency covers both sides. The Texas State Board of Plumbing Examiners (TSBPE) licenses individual plumbers and tracks the Responsible Master Plumber (RMP) who anchors each plumbing business. Use the TSBPE Public License Search at tsbpe.texas.gov, searchable by name, license number, or location.

The tiers follow a strict hours ladder:

• Plumber's Apprentice: a registration, not a license. Apprentices work only under supervision while logging hours toward the next tier.
• Tradesman Plumber-Limited: at least 4,000 hours of plumbing experience plus a 24-hour TSBPE-approved training course and an exam. Scope is limited, generally to one- and two-family dwellings, under an RMP.
• Journeyman Plumber: at least 8,000 hours of documented experience plus a 48-hour training course and an exam. Journeymen perform broader plumbing work but still work under an RMP when the work is contracted to the public.
• Master Plumber: built on journeyman experience (two years as a journeyman, or one year after an approved apprenticeship) plus an exam. Only a master can hold the RMP designation.
• Responsible Master Plumber (RMP): a designation, not a separate license. Texas law requires that a person or company offering plumbing services to the public secure the services of at least one RMP, with a current certificate of insurance on file with TSBPE.

The common Texas mistake is accepting an individual credential as a business license. A journeyman or master card proves the person is qualified to do the work, not that a business is authorized to contract for it. Confirm the RMP is tied to the company on your contract, the insurance certificate is current, and the disciplinary history is clean.

How do you verify a plumber license in Washington?

Washington layers the check, which is why it confuses people. A construction business registers with the Department of Labor and Industries (L&I), but that registration is not a plumbing certification. Start with L&I's Verify a Contractor, Tradesperson or Business service, which surfaces registration, bond, insurance, workers compensation, and trade credentials, then confirm the plumbing certification itself rather than stopping at an active registration.

The individual ladder starts with a Plumber Trainee certificate, which permits work only under the direct supervision of a certified plumber. The broad credential is the Journeyman Plumber (PL01) certification: at least 8,000 hours of supervised experience over four years, including at least 4,000 hours in commercial or industrial installations, plus classroom training, followed by a closed-book exam on the Uniform Plumbing Code with Washington amendments. A passing score of 70% is required. The Residential Specialty Plumber (PL02) certification requires at least 6,000 hours and covers residential work only, so a PL02 on a commercial job is a scope mismatch.

Here is the trap: a trainee certificate, a specialty certification, and a journey-level certification all look alike on a resume, but only the matching tier authorizes the work in front of you. Verify the PL01 certification in the L&I record, and check that the business registration names the same entity as your contract. Washington's reciprocity is narrow, so do not accept an out-of-state license as a substitute for Washington certification.

What red flags should stop a hire in any state?

• No record found. The number or name returns nothing in the official lookup. Treat this as unlicensed until proven otherwise.
• Expired, suspended, or revoked status. Only an active record authorizes work. Do not accept "renewal in progress" as a substitute.
• Wrong tier for the scope. A residential-only credential on a commercial job, a trainee working unsupervised, a tradesman-limited license outside dwellings, or a specialty certification outside its scope.
• Business record without the individual, or individual without the business. In all three states, hiring requires both sides to check out. In California the business record carries the weight; in Texas and Washington the individual credential must match it.
• Name mismatch. The entity on the contract is not the entity on the license or the insurance certificate. Pay only the licensed business.
• Lapsed bond or insurance. In California, confirm the $25,000 contractor bond is on file. In Texas, confirm the RMP certificate of insurance is current with TSBPE. In Washington, confirm the registration bond and liability insurance are current in the L&I record.
• Out-of-state credential only. Plumbing credentials do not transfer automatically. A Texas journeyman still needs California or Washington credentials to work in those states, and vice versa.

Frequently asked questions

Is it free to verify a plumber license?

Yes, in all three states. The CSLB, TSBPE, and L&I lookups are free and public, and none requires an account.

Can one person hold the license and another do the work?

Yes, as long as both credentials are valid. The business holds the contracting license, a qualifying individual anchors it (the RMP in Texas, the certified plumber in Washington, the qualifier in California), and the worker on site holds the certification for the scope performed.

What if the plumber is licensed in another state?

Do not assume reciprocity. Check the state where the work will be performed, every time. Washington's recognition is narrow, and California and Texas each require their own records.

How often should a business recheck a plumber's license?

At onboarding, at every renewal anniversary, and before the next payment on a long project. A credential active at onboarding can lapse mid-project. Our contractor onboarding verification checklist pairs the license check with identity, insurance, bond, W-9, and sanctions, and our electrician license verification guide follows the same two-record pattern for the electrical trade.

How do I automate plumber license checks at scale?

Manual lookups work for one hire. They break at volume: a two-minute check times hundreds of vendors is a full-time job, and records change between onboarding and the next project phase. StateLicense's API reads the same official state records in bulk, on a schedule, so an expiration or suspension surfaces before the next payment goes out.

Quick checklist before you hire a plumber

1. Get the business license number and the individual certification or license number.
2. Search the official state lookup: CSLB in California, TSBPE in Texas, L&I in Washington.
3. Confirm the business record is active, covers plumbing work, and names the entity on your contract.
4. Confirm the individual credential is active and matches the scope: apprentice versus tradesman versus journeyman versus master in Texas, trainee versus residential specialty versus journey level in Washington.
5. Confirm bond and insurance are current and under the same business name.
6. Check the enforcement or discipline history before signing a large contract.
7. Recheck at renewal dates and before the next payment on longer projects.

A plumber license check is a two-record habit: business plus individual, in the state where the work happens, on the day you hire.