Missouri to Delaware: master plumber license reciprocity

Delaware issues a person-held Master Plumber license through the Board of Plumbing, Heating, Ventilation, Air Conditioning and Refrigeration Examiners in the Division of Professional Regulation. 24 Del. C. § 1807 requires that license (or a statutory exemption) to provide plumbing services or to use the titles licensed plumber / master plumber. Employees, apprentices and journeymen work under a master's supervision without their own Board license. A new master needs a journeyman's certificate from a federally-standard apprenticeship plus two years under a master plumber (or similar-level licensee in another state), or seven years under such supervision plus the Delaware vocational-technical apprenticeship equivalency tests, then Board approval and the ProV-administered master plumber exam; the application fee is $173. Out-of-state masters apply by reciprocity under 24 Del. C. § 1810 without a Delaware exam: the Board shall grant the license if the origin state's standards are substantially similar, and otherwise requires at least seven years of practice after licensure. 24 DE Admin. Code 1800 § 2.3 requires every reciprocity applicant to submit the origin state's licensure laws and regulations so the Board can make that comparison. Licenses renew biennially; from the 2026 renewal, plumbing licensees complete 5 hours of continuing education (3 code, 1 safety, 1 cross-connections/backflow) by October 31 of even-numbered years.

Missouri issues no statewide master plumber or plumbing contractor license. RSMo chapter 341 leaves plumber licensing to cities over 15,000 and first-classification counties, whose boards examine master plumbers, set fees and license terms and (in counties) require master plumber and master drainlayer surety bonds; no state agency licenses the trade and the voluntary statewide contractor license that exists for electrical work has no plumbing counterpart. The master credential therefore exists only locally: Springfield's Master Plumber certification (4 years as a certified journeyman or 10 years' experience, ICC exam, $50), Kansas City's plumbing contractor license qualified by a supervisor holding a certificate of qualification (Prometric or ICC exam, $60 application, $181 four-year renewal; contractor license $55 application, $181 issuance), St. Louis County's Master Plumber license and certified contractor list, and the City of St. Louis Plumbers and Drainlayers Board of Examiners' master plumber and drainlayer licenses. An out-of-state master plumber license carries no state-level recognition; Springfield accepts an identical ICC, Prometric, Experior or Block exam score of 75% or better in place of retesting and Kansas City may accept a comparable exam it deems equivalent, while the St. Louis County and City of St. A master arriving from another state should expect to qualify in each jurisdiction separately and then obtain that jurisdiction's contractor license and bond to pull permits.