How to Become a Plumber in Missouri: Licenses, Exam, and Fees

To become a plumber in Missouri, you work up through three levels — apprentice, journeyman, then master — and apply for a license from the city or county board where you plan to work. Missouri does not issue a statewide plumbing license. The Missouri Division of Professional Registration handles many trades, but not this one. Cities of 15,000 or more require plumbers to apply to a local board of examiners and pass an exam before working in the trade.¹ The state’s Uniform Plumbing Code applies only in first-class counties that have formally adopted it.²

The practical consequence: a license from one Missouri jurisdiction does not automatically let you work in another. If your jobs will cross city or county lines, plan on separate licenses in each place.

The Three License Levels

Missouri recognizes three tiers, and you move through them in order.

Apprentice. The entry level. Apprentices work under the direct supervision of a licensed master plumber and are not licensed in the traditional sense. Most jurisdictions register apprentices rather than testing them. Kansas City registers apprentices through its Department of Planning and Development; St. Louis registers them through its Board of Plumbing Examiners.

Journeyman. A journeyman can perform plumbing work independently. Under the state statute, a journeyman applicant must be at least 21 and have at least five years of apprentice experience under a licensed master plumber.³

Master. The highest classification. A master plumber can direct other plumbers, design systems, pull permits, and run a plumbing business. Under state statute, a master plumber applicant must be at least 25 and have at least three years of experience as a licensed journeyman.³

Local jurisdictions sometimes set different experience thresholds. St. Joseph requires three years for a journeyman license and four for a master, with experience verified through notarized written references.⁴ Check the actual rules in the jurisdiction where you plan to apply. The statute is the floor, not the ceiling.

Documenting Your Experience

Applications stall more often on experience paperwork than on anything else. Keep records from day one of your apprenticeship: employer names, dates, hours, and the name of the licensed master who supervised you.

Most jurisdictions require notarized written references or employer affidavits verifying your work history. St. Louis County requires third-party verification and an affidavit of employment experience if you are not currently registered as an apprentice in its system. If a former employer has closed or is unreachable, notarized affidavits from licensed plumbers who supervised you directly can sometimes fill the gap.

Many local boards also run criminal background checks. A felony conviction related to the trade can delay or prevent licensure, though most boards review these individually.

The Licensing Exam

Every jurisdiction that licenses plumbers requires an exam. Formats differ. Under the state statute, the exam has two parts: written and practical.⁴ Kansas City uses standardized computer-based exams from the International Code Council (ICC).⁵

Content is fairly consistent: plumbing code, installation methods, drainage and venting principles, fixture sizing, and safety practices. Master exams add system design, project planning, and supervision.

Passing scores vary. St. Joseph requires 70 percent for journeymen and 76 percent for masters.⁴ Under the state Uniform Plumbing Code, an applicant who fails must wait 90 days before reapplying and must pay the application fee again.⁶ Some cities set their own retake limits.

To prepare, study the plumbing code your jurisdiction actually enforces. Many Missouri cities and counties use versions of the International Plumbing Code, but some use locally modified codes. Ask your local board which edition applies. The written portion trips up experienced plumbers because it tests code knowledge, not hands-on skill.

Fees, Bond, and Insurance

Application and licensing fees are set locally. The state statute lists nominal application fees of $10 for a master and $2 for a journeyman, with a one-year license term.⁶ Local fees run higher in practice. St. Charles County charges $200 for a two-year license; Jefferson City charges a $33 renewal fee. Expect somewhere between roughly $30 and $200 depending on jurisdiction, license type, and cycle.

Under the state Uniform Plumbing Code, a master plumber must file a $2,000 surety bond before receiving a license. The bond guarantees compliance with plumbing regulations and covers damage or injury caused by negligent work.⁷ Some local jurisdictions require more.

Missouri sets no single statewide minimum for plumber liability insurance. Requirements come from local licensing authorities, and most commercial projects and many municipal offices expect at least $1 million per occurrence in general liability coverage.

Workers’ compensation deserves special attention. Missouri’s general threshold is five or more employees, but construction employers who build, demolish, alter, or repair structures must carry workers’ compensation with one or more employees.⁸ Plumbing contractors fall in that category. Hire one helper and you need coverage.

Licensing in the Major Cities

Missouri’s largest metros run their own programs.

Kansas City

The Permits Division within City Planning and Development handles contractor licensing. Plumbers need a business license from the Finance Department and then apply for a Certificate of Qualification in their trade. The city uses ICC exams and sets its own insurance rules in Information Bulletin IB135.⁵

City of St. Louis

Plumbing contractors must hold a license from the city’s Building Division. The city issues plumbing permits only to licensed contractors, and applicants must pass a test administered by the Board of Examiners covering code knowledge and mechanical skill. The permit application fee is $30.⁹

St. Louis County

The county has a separate Board of Plumbing Examiners. Journeyman applicants submit a photo, state-issued ID, and either verification of apprentice registration or an affidavit of employment experience with third-party verification. The county tracks continuing education through Professional Education Units on a three-year license cycle.

Call the local office before you start any application. Documentation, exam scheduling, and fees differ enough between jurisdictions that assumptions carried over from one to another cost time and money.

Renewal and Continuing Education

Renewal cycles and continuing education requirements vary. Some jurisdictions renew annually, some every two years, some every three. St. Charles County uses a two-year cycle with licenses expiring in odd years. Common continuing education topics include plumbing code updates, cross-connection control and backflow prevention, safety practices, and installation techniques. Your local board can tell you the exact hours and approved providers.

Take the deadline seriously. Under the state Uniform Plumbing Code, letting your license lapse means starting the examination process over as a new applicant.⁶ Some local jurisdictions impose late fees instead of requiring reexamination, but either way, missing the date costs you.

Military Fee Waivers and the Plumbing Carve-Out

Missouri waives all occupational licensing fees for two years after application approval for active duty service members, their spouses, honorably discharged veterans, and their spouses. The licensing authority must process fee waiver applications within 30 days.¹⁰

One catch matters for plumbers. Missouri law generally lets military spouses skip examination, education, and experience requirements when transferring a license from another state. Plumbing is specifically excluded from that waiver.¹⁰ Military spouses with plumbing licenses from other states get the fee waived but still have to meet the local exam and experience rules. Bond and insurance requirements are not waived either.

Out-of-State Licenses

Missouri has no formal statewide reciprocity agreements that let out-of-state plumbers transfer licenses automatically. If you hold a plumbing license from another state, plan on applying fresh in whichever Missouri jurisdiction you want to work in, meeting its experience requirements, and passing its examination.

House Bill 2394, introduced in the 103rd General Assembly, would create provisions for plumbing license reciprocity. The bill was prefiled in December 2025 with a proposed effective date of August 28, 2026.¹¹ Whether it passes and in what form is uncertain. Check its status if reciprocity matters to your plans.

Even without formal reciprocity, some local jurisdictions accept ICC exam scores from other states. If you already hold an ICC certification, ask the local licensing board whether they will accept it in place of their own exam.

1
Missouri Revisor of Statutes. Missouri Code 341.020 – Examination Required in Cities of Certain Population
2
Missouri Revisor of Statutes. Missouri Code 341.100 – Uniform Plumbing Code, Application
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Missouri Revisor of Statutes. Missouri Code 341.170 – Qualifications of Applicants for Master Plumber’s License
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St. Joseph, MO. Application for Master/Journeyman Plumbing Examination
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CITY OF KANSAS CITY. Contractor Licensing
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Missouri Revisor of Statutes. Missouri Code 341.180 – Fees With Applications for Licenses, Term of Licenses, Reexaminations
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Missouri Revisor of Statutes. Missouri Code 341.200 – Master Plumber and Master Drainlayer Shall Deposit Surety Bonds, Amount
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Missouri Division of Workers’ Compensation. Who Is Required to Carry Workers’ Compensation Insurance Coverage
9
City of St. Louis. Apply for a Plumbing Permit
10
Missouri Revisor of Statutes. Missouri Code 324.009 – Military Licensure, Definitions, Requirements
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Missouri House of Representatives. HB 2394 – Creates Provisions Relating to Licensure Reciprocity for Plumbers