You get a St. Louis County plumbing license from the county itself: Missouri issues no statewide plumbing license, and St. Louis County licenses journeyman and master plumbers through its Department of Transportation and Public Works plumbing licensing office.
You apply to that office with the documents and qualification requirements it lists — our research did not capture the county's hours, fees or exam details, so confirm them with the office before you apply.
Why Missouri licenses plumbing locally
Missouri has no statewide plumbing license.
The Missouri Division of Professional Registration's list of state licensing boards includes Electrical Contractors but no plumbing, mechanical or HVAC board, so there is no state application to file, no state exam to schedule and no state fee to pay — the state issues no plumbing license at all.
The licensing that matters happens where you work.
St. Louis County runs its own system: the county licenses journeyman and master plumbers through its Department of Transportation and Public Works plumbing licensing office, and the same office issues backflow (BFD) tester certificates.
Kansas City is the other local system our research verified — the city issues Journeyman Plumber and Master Plumber certifications, required for individuals performing or supervising plumbing work in the city.
One geography note before you apply anywhere: a search for a St. Louis plumbing license could describe a credential from St. Louis County or from the City of St. Louis, and our research covered the county's plumbing licensing only — the City of St. Louis is a separate jurisdiction our research did not cover.
If you will work inside city limits, ask the city's building or licensing department what it requires before you work there.
The statewide picture — how licensing works across Missouri, and what our research could not confirm about reciprocity — is on our Missouri plumbing license guide.
The national ladder of apprentice, journeyman and master credentials is explained in our plumbing license requirements guide.
What are the county's requirements, and is there an exam?
The county's plumbing licensing office handles both levels: journeyman plumber and master plumber.
Its page lists the documents, information and qualification requirements for becoming a journeyman or master plumber, and that page — not a summary on another site — is the authority on what to submit.
Our research did not capture the numbers behind those requirements: no experience hours, no ages, no fees, and no confirmation of whether the county tests plumbing applicants or which vendor would run the exam.
We would rather name the gap than fill it with a figure from a guide that cannot show its source.
Because Missouri has no state plumbing license, any hour total or fee quoted for a "Missouri state" plumbing license cannot be a state requirement — check whatever number you find against the county office.
What the research did capture is how the county runs licensing on the mechanical side, which shows the system's shape.
St. Louis County operates a Board of Examiners for Mechanical Licensing, also under the Department of Transportation and Public Works, whose journeyman mechanical licenses require continuing education (PEU credits) for renewal.
Under that board's Rule IV, effective June 17, 2025, an approved journeyman mechanical applicant must take the test within one year of approval — a 90-day extension may be granted — and may retake it as often as needed within that year.
Our research captured these rules for mechanical licenses, not for the plumbing licenses, so ask the plumbing office whether its process carries an equivalent exam window.
Once you hold the county credential, browse the plumber jobs on our board to see what employers are hiring for.
Confirm the requirements with the county office
How do you look up a St. Louis County plumbing license?
There is no statewide Missouri plumbing license lookup, because there is no statewide license to look up — the record sits with the office that issued the credential.
For this county, that is the plumbing licensing office: the county is one of the local offices our research names as the place to check when no state lookup exists.
Our research notes St. Louis County publishes lists of licensed master plumbers on stlouiscountymo.gov.
That note comes from our research vault rather than one of our verified facts, so treat it as a starting point — confirm the current address, and any individual record, with the plumbing licensing office itself.
If you are hiring, or working for, someone claiming a county credential, the same rule applies: ask the office that would have issued the license to confirm it.
A printed card or a certificate on an office wall is not a lookup.
Career information, not legal advice. Licensing requirements change; confirm the current St. Louis County plumbing licensing requirements with the county's plumbing licensing office — and with any other city or county where you will work — before you apply for or rely on a license.