Plumbing is a licensed trade with specialty certifications layered on top. This overview covers the journeyman → master → contractor license ladder, plus medical-gas, backflow-tester and plumbing-design credentials.
Plumbers progress through a state license ladder — apprentice → journeyman → master → contractor — based on documented experience and code-based exams. Specialties such as medical-gas installation, backflow-prevention testing, and plumbing design (CPD) or a Mechanical PE add scope for specific work.
The core working-plumber license to install and repair plumbing systems.
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Advanced license to design installations and supervise journeymen.
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License to operate a plumbing business, pull permits and bid work.
Certification to install or inspect medical gas and vacuum systems.
Certification to test and certify backflow-prevention assemblies.
Design credentials for engineers and designers of plumbing systems.
| Credential | Prerequisite | Typical experience | Administered by |
|---|---|---|---|
| Journeyman Plumber | Apprenticeship | ~4–5 years* | State / local board |
| Master Plumber | Journeyman license | Several years* | State / local board |
| Plumbing Contractor | Master (often) | Experience + business* | State board |
| Medical Gas (ASSE 6010) | Piping background | Training + brazing* | ASSE |
| Backflow Tester (ASSE 5110) | Approved course | Written + practical* | ASSE / state |
* Experience hours and prerequisites vary significantly by state, jurisdiction and credential level. Figures shown are typical ranges, not legal requirements.
Journeyman and master exams are open-book and time-pressured. A well-tabbed UPC or IPC (whichever your state adopts) — sizing tables, venting, fixture units — is the biggest time-saver.
Water-supply and DWV sizing, fixture-unit counts, and gas-pipe sizing recur. Drill them — and rehearse with the studio’s tools.
Medical-gas and backflow certifications include hands-on practicals (brazing, assembly testing). Build the manual skills, not just the written knowledge.
Confirm the exact education, experience hours and application steps with the certifying body or state board first — missing a prerequisite trips up more people than the exam content does.
You generally complete a ~4–5 year apprenticeship (~7,500–8,000 hours plus classroom), pass the Journeyman Plumber exam, gain several years of licensed journeyman experience, then pass the Master Plumber exam. Requirements vary by state and locality.
Most journeyman and master plumbing exams are open-book using the adopted plumbing code (UPC or IPC) and state amendments. They are computer-based and time-pressured, so fast code lookup matters.
Medical gas installation requires ASSE 6010 (installer) certification, with inspection/verification covered by ASSE 6020/6030; the work follows NFPA 99 and requires brazing qualification. It is a specialty layered on a plumbing/pipefitting background.
A Backflow Prevention Assembly Tester certification (commonly ASSE 5110) certifies you to test and certify backflow-prevention assemblies. It involves an approved course plus written and hands-on practical exams, and is often required to perform tests for water utilities.
Many exam questions are calculation problems you can rehearse right now with the free tools in the Plumbing Systems Studio: