Maryland plumber license: requirements, reciprocity & renewal

The master license in Maryland

Master Plumber/Gas Fitter: Hold a journey license for at least 2 years + complete 3,750 hours of training under the direction and control of a licensed master plumber + pass a comprehensive written examination with a score of at least 75% (Maryland OneStop master license page). Maryland OneStop lists the master application cost as $70.

To contract/provide plumbing services the master must carry liability insurance of at least $300,000 general liability plus $100,000 property damage per occurrence ($400,000 combined minimum per occurrence; umbrella coverage not acceptable) with the Maryland State Board of Plumbing as certificate holder — Board insurance page, labor.maryland.gov.

Renewal & lapse in Maryland

Licenses expire 2 years from date of issue. The Board's renewal page states that a licensee who lets a license lapse and fails to renew for more than 4 years must file a new application and pass the appropriate examination.

Reinstatement: Within 4 years of expiration the license can still be renewed/reinstated through the Board's renewal process (Board mails/e-mails a renewal notice about 60 days before expiration).

Past the line: Lapsed more than 4 years: file a new application and pass the appropriate examination — the old license cannot simply be renewed (Maryland Board of Plumbing renewal page, labor.maryland.gov, accessed 2026-10-22).

Expired? Run the renewal checker with your month count →

Opening a plumbing company in Maryland

The seat: Master Plumber / holder of a Limited Master Plumber license designated to direct and control the business. Under Md. Code, Business Occupations and Professions §12-504, every plumbing advertisement for a business must contain the license number and name of a master plumber (or limited master holder) the business employs and designates to direct and control the provision of plumbing services. A journey plumber may only provide plumbing services under the direction and control of a master.

Insurance minimum: $300,000 general liability + $100,000 property damage per occurrence ($400,000 combined minimum per occurrence)

The State Board does NOT license in Baltimore County or in the areas served by the Washington Suburban Sanitary Commission (WSSC — Prince George's County and parts of Montgomery County). Those two jurisdictions issue their own plumbing licenses and enforce their own plumbing code (Maryland OneStop / Board FAQ).

Run the owner gate for your situation →

Sources

Rules as published by Maryland State Board of Plumbing, Department of Labor, Division of Occupational and Professional Licensing and the statutes it administers, checked October 22, 2026. Board: https://www.dllr.state.md.us/license/pl/pllicfaqs.shtml

• COMAR 09.20.02.02 — Required Training for Apprentice Plumbers (7,500 hours), Maryland Regulations
• Renew or Reinstate Your License — Maryland Board of Plumbing (2-year expiry; >4 years lapsed = new application + exam)
• Insurance Requirements — Maryland Board of Plumbing ($300,000 / $100,000)
• Licensing FAQs — Maryland Board of Plumbing (reciprocity: Delaware, WSSC, Baltimore County ONLY)
• Master Plumber/Gas Fitter License — Maryland OneStop (2 years journey + 3,750 hours + 75% exam; $70 application cost)
• Apprentice Plumber/Gas Fitter License — Maryland OneStop (Baltimore County / WSSC exclusion)