Delaware Plumber License Reciprocity: Which States Transfer and Which Don't

Delaware Does Not Have Universal Reciprocity

If you hold a master plumber license in another state and want to work in Delaware, reciprocity is not automatic. The Board of Plumbing Examiners evaluates each state's licensing standards individually and classifies them as either "substantially similar" to Delaware's or not. Your path depends entirely on which category your home state falls into.

States With Direct Reciprocity

Delaware currently recognizes three states as having substantially similar plumbing licensing standards:

• Connecticut
• Iowa
• Maryland

If you hold an active master plumber license from one of these states, you can apply through DELPROS for Delaware licensure without taking the master plumber exam. You still need to submit your application, provide verification of your out-of-state license, and pay the $173 state application fee — but the exam requirement is waived.

Maryland reciprocity is the most commonly used path, given the geographic proximity and the number of plumbers who work across the Delaware-Maryland border.

States Without Direct Reciprocity

Applicants from states whose licensing standards are deemed "not substantially similar" face a more demanding process. This includes New Jersey, most southern states, and most other jurisdictions. Pennsylvania is handled separately because its licenses are municipal, not statewide.

For non-similar statewide license holders, Delaware offers two options:

Option 1: Document at least seven years of active master-level practice in your home state. This means seven years of holding a master license and actively working as a master plumber — not seven years of total experience. If the Board accepts your documentation, you may be exempted from the Delaware exam.

Option 2: Submit your home state's licensing laws and exam requirements for formal Board evaluation. The Board reviews these at a monthly meeting and decides whether your state's standards are close enough to qualify for a waiver.

If neither option produces a waiver, you take the Delaware master plumber exam through ProV — the same exam that in-state candidates face.

Why Pennsylvania Is Specifically Excluded

Pennsylvania gets special treatment in Delaware's reciprocity rules, and not in a good way. PA plumbing licenses are issued by individual municipalities, not by a centralized state board. Because there is no single statewide licensing standard in Pennsylvania, Delaware's Board has categorically excluded PA from direct reciprocity.

If you hold a Philadelphia, Pittsburgh, or any other municipal plumbing license from Pennsylvania, you must apply by examination. No amount of PA experience substitutes for the fact that Delaware does not recognize municipal licenses as equivalent to state-level credentials.

The DELPROS Application for Reciprocity

Reciprocity applicants use the same DELPROS portal and face the same 180-day application timeout as in-state candidates. You need to submit:

• Active out-of-state master plumber license documentation
• A verification letter from your home state's licensing board
• Evidence of post-licensure practice (for non-substantially-similar states)
• The $173 non-refundable application fee

The Board reviews reciprocity applications at monthly meetings. Straightforward applications from Connecticut, Iowa, or Maryland tend to process within one meeting cycle. Applications requiring Board evaluation of an unfamiliar state's standards can take longer.

Delaware vs. Maryland: Key Differences

Maryland and Delaware are the most common cross-border comparison. Both states require a master plumber license for independent practice, and both recognize each other through reciprocity. The main structural difference is that Maryland's exam is administered through PSI (not ProV), and Maryland's apprenticeship requirements and CE rules differ in specifics — but the Board considers the overall standards substantially similar.

Delaware vs. Pennsylvania: Key Differences

The fundamental difference is structural. Delaware has one statewide licensing system through DPR. Pennsylvania has no statewide plumber license — licensing happens at the city and county level, with each municipality setting its own standards. A Philadelphia master plumber license means nothing in Pittsburgh, and neither means anything to Delaware's Board.

If you are moving from PA to DE, plan on taking the Delaware exam. There is no workaround for this, regardless of how many years of PA experience you have.

The Delaware Plumber License Guide includes a reciprocity application navigator that helps you determine which pathway applies to your state and what documentation the Board will need.

See more Delaware guides →