Washington 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.

Washington has no master plumber license. WAC 296-400A-010 lists every certificate the state issues (journey level PL01, residential PL02, residential service PL04, pump and irrigation PL03, domestic well PL03A, backflow PL30, and trainee), and the Journey Level Plumber certificate is the highest credential an individual can hold; the only add-on is the Medical Gas Piping Installer endorsement (MG01), which is a specialty, not a supervisory tier. Since July 1, 2021 a business that advertises, bids or performs plumbing work must hold a Plumbing Contractor license under RCW 18.106.400, but that is a business registration rather than a person-held trade license: the firm registers with the Department of Revenue, files a $6,000 surety bond, carries $250,000 combined (or $200,000/$50,000) liability insurance, pays a $148.10 license fee plus $53.20 to designate a Washington-certified plumber who works for the firm full time, and renews every two years; no exam is taken by the owner. An out-of-state master plumber therefore has nothing to transfer to at this level. To work as a plumber they obtain the journey level (PL01) certificate through the journeyman path (Idaho reciprocity or license review plus the Washington exam), and to contract they form a business and license it as a plumbing contractor with themselves or an employee as the designated certified plumber.