Plumber License: Delaware vs Maryland vs Pennsylvania

Three Neighboring States, Three Different Licensing Systems

Plumbers working in the Delaware/Maryland/Pennsylvania tri-state area quickly discover that licensing doesn't transfer the way a driver's license does. Each state structures its plumbing regulation differently, and those structural differences determine whether your license crosses state lines smoothly or requires starting the application process from scratch.

Delaware licenses plumbers through a centralized state board — the Board of Plumbing, Heating, Ventilation, Air Conditioning and Refrigeration Examiners under the Division of Professional Regulation. Maryland also uses a centralized state board. Pennsylvania, by contrast, has no statewide plumber licensing — it's handled at the municipal level.

That last point is the source of most reciprocity confusion for plumbers moving between these states.

Delaware to Maryland: Reciprocity Exists

Maryland is one of the states Delaware classifies as having "substantially similar" standards. Licensed Master Plumbers from Maryland can apply for a Delaware license through the reciprocity pathway, potentially bypassing the Delaware exam entirely.

The process involves submitting your active Maryland license, documentation of your training and experience, and the standard DELPROS application with the $173 state fee. The Board reviews reciprocity applications at their monthly meetings.

Going the other direction — Delaware to Maryland — follows a similar reciprocity arrangement. Maryland's State Board of Plumbing recognizes Delaware's centralized licensing standards.

The practical takeaway for plumbers working both sides of the Delaware-Maryland border: getting licensed in one state positions you well for reciprocity in the other. The administrative lift is significantly lower than applying as a new candidate.

Pennsylvania to Delaware: No Direct Reciprocity

This is where plumbers run into trouble. Delaware's Board specifically excludes Pennsylvania from direct reciprocity because PA doesn't have a centralized state plumbing board. Pennsylvania plumbing licenses are issued by individual municipalities — Philadelphia, Pittsburgh, and other cities each run their own licensing systems.

Because there's no single PA state standard for the Board to compare against, Delaware excludes Pennsylvania from direct reciprocity. A PA plumber applying in Delaware must apply by examination.

Submit a standard DELPROS application, get Board approval, and take the ProV Master Plumber exam — the same process as any Delaware-based candidate. You'll still need to document your experience through Verification of Employment forms or W-2 alternatives. The seven-year no-exam path that applies to some other out-of-state license holders does not substitute for the exam when the underlying credential is a municipal Pennsylvania license.

The exam itself is a 3-hour, 100-question, open-book test with a 70% passing threshold.

Key Differences in How Each State Works

Beyond reciprocity, the three states differ in several ways that affect day-to-day operations:

Permitting structure. Delaware and Maryland both split permitting between state health departments and local municipalities. Pennsylvania's permitting is entirely local. A plumber working across all three states needs to navigate different local permitting systems in each.

Continuing education. Delaware is implementing a 5-hour biennial CE requirement starting with the October 2026 renewal cycle. Maryland has had CE requirements in place for years. Pennsylvania's CE requirements vary by municipality — some require it, others don't.

Insurance minimums. Delaware requires $100,000 per occurrence general liability and $300,000 per occurrence property damage for contractor registration. Maryland and Pennsylvania requirements vary but typically fall in a similar range.

Exam vendors. Delaware uses ProV for its licensing exam. Maryland uses PSI. Pennsylvania doesn't have a state exam — municipal exams vary by jurisdiction.

Planning a Multi-State Practice

For plumbers who want to work across the tri-state area, the most efficient path is to get licensed in Delaware or Maryland first. Both states have centralized boards with reciprocity agreements, so one license can leverage into the other relatively quickly.

Pennsylvania licensing, because it's municipal, needs to be handled jurisdiction by jurisdiction. There's no shortcut — each city where you want to pull permits requires its own application.

The Delaware Plumber License Guide covers the reciprocity application process in detail, including which states qualify for direct recognition and what documentation the Board requires from out-of-state applicants.

See more Delaware guides →