How Do I Know a Plumber Is Legit in Minnesota?

A Minnesota plumber should show you two kinds of credentials. The business holds a plumbing contractor license. Each person on the job holds a personal credential, or works as a registered unlicensed plumber under a licensed plumber. This guide explains each one and how to check it before you hire.

Six checks before you hire

1. The business license. Ask for the plumbing contractor license number. Town size decides whether the business needs a plumbing contractor license or a restricted one. See below.
2. The responsible licensed individual. For a plumbing contractor, DLI requires an active master plumber as the responsible licensed individual. Ask who that is.
3. The bond. For a plumbing contractor, DLI requires a $25,000 surety bond. DLI says it can call on that bond to correct work that does not meet code. The DLI pages we read do not say whether a restricted plumbing contractor has the same requirement. Ask DLI.
4. The insurance certificate. Ask to see it. For a plumbing contractor, DLI requires products liability of at least $50,000 per person and $100,000 per occurrence, and property damage of at least $10,000. The business name must match its Secretary of State filing exactly.
5. The truck. The company’s license number must appear on all company vehicles.
6. Every employee. Each one who does plumbing work must be licensed, registered as an unlicensed plumber, or enrolled in a registered apprenticeship. A pipelayer’s card covers exterior pipe work only.

The business license: plumbing contractor or restricted

DLI says businesses and individuals that contract to do plumbing work need one of two licenses. Town size decides which one:

• A plumbing contractor license is required for plumbing work in communities with a population over 5,000. DLI’s license types page says a plumbing contractor may contract “in all areas of the state,” with a master plumber as responsible individual.
• A restricted plumbing contractor cannot contract to perform work in communities over 5,000.

Employees of a licensed plumbing contractor, and general contractors that hire licensed subcontractors, do not need their own plumbing contractor license. Ask for the plumber’s license number either way.

Plumbing contractor licenses expire on December 31 of odd-numbered years. DLI lists the initial application and renewal fee as $188.

What each personal credential allows

Credential	Who holds it	What it allows	Limits
Master plumber	Five or more years of practical work experience.	Statewide work on interior plumbing and exterior water, sanitary and storm sewer within property lines. Bids on jobs of any size and may design systems.	None stated.
Journeyworker plumber	Passes the exam after four years and at least 7,000 hours of practical work.	Statewide work on interior plumbing and exterior systems within property lines.	Works under a master plumber’s direction. See the note below.
Restricted master plumber	Four years of practical experience, or two years as a plumbing contractor. DLI says the four years had to be documented before Oct. 1, 2008.	Work on interior plumbing and exterior systems within property lines, in cities and towns with a population of fewer than 5,000 according to the most recent federal census.	Only in cities and towns with fewer than 5,000 people.
Restricted journeyworker plumber	At least two years of practical experience, documented before Oct. 1, 2008.	The same work as a restricted master, under a restricted master’s direction.	Only in cities and towns with fewer than 5,000 people. The Choosing a plumber page says it may work without on-site supervision only in cities under 5,000.
Registered unlicensed plumber	Registered with DLI, the starting position for aspiring plumbers.	Plumbing work as an employee.	Must work under direct supervision. See the note below.
Certified pipelayer	A “pipelayer’s card” from pipe-laying training.	Water service, building drain and sewer, and storm sewer within property lines.	Not inside buildings. Not interior plumbing.

Three points need care:

• Journeyworker direction. The pages differ. The Choosing a plumber page says a journeyworker in a city over 5,000 must work under a master plumber’s direction, and that a journeyworker “may work without on-site supervision.” The license types page says a journeyworker works under a master plumber’s direction, with no population limit. Ask who directs the work on your job.
• Restricted journeyworker direction. The license types page says a restricted master plumber directs them. The Choosing a plumber page says a master plumber or a restricted master plumber. The DLI pages we read do not settle it.
• Who may supervise a registered unlicensed plumber. The Choosing a plumber and licensing basics pages name a licensed journeyworker or master plumber. The license types page also lists a restricted master, a restricted journeyworker or a plumbing contractor.

A registered unlicensed plumber is not the same as a construction contractor registration. Our licensed, registered, bonded and insured guide covers that registration.

Who supervises unlicensed workers

DLI says Minnesota’s plumbing laws require unlicensed plumbers to be directly supervised by a licensed plumber. DLI says Minnesota Statute 326B.42, subdivision 2, defines direct supervision. Under that definition:

• The supervising plumber must be at the work location whenever the unlicensed worker is doing plumbing work.
• The supervising plumber must be physically present and immediately available.
• Electronic supervision does not count.
• The supervising plumber reviews the work before the plumbing is operated.

DLI also says an unlicensed worker can be supervised only by a licensed plumber employed by the same company. Contractors must keep records of unlicensed workers’ experience.

Plumbing permits and inspections

Who gets the permit. DLI puts the duty on the licensed plumbing contractor. It must obtain plumbing permits and submit plans for review when required, at or before the start of the work. The DLI pages we read do not say whether a homeowner can pull a permit. Ask DLI at 651-284-5063 or the local administrative authority.

Plan review. Plans and a fee are required for systems that serve the public or a considerable number of persons. DLI’s examples include restaurants, hotels and “housings with five units or more, such as apartments and condominiums.” DLI says its list is not complete. For plan review and permit questions, email iMS.bldplb.dli@state.mn.us or leave a voicemail at 651-284-5063.

Inspections. The contractor “should notify the proper administrative authority at least eight hours before the work is to be inspected or tested.” Who inspects depends on the building:

• For state-licensed facilities, public buildings and projects of a special nature, DLI says it inspects in non-code-enforced areas. In code-enforced areas, DLI inspects where the municipality lacks both a plumbing plan review agreement with DLI and a licensed plumber to do the inspections.
• For all other building types, which includes homes, DLI says it inspects in non-code-enforced areas. In code-enforced areas, DLI inspects where the municipality does not have a licensed plumber or someone meeting the competency requirements to perform the inspections.

Otherwise, notify the local administrative authority. DLI’s page links to a way to locate it. Where there is no local inspection department or building official, DLI says to contact its regional plumbing standards representative.

How to check a plumber’s license

1. Get the business’s plumbing contractor license number. Ask who its responsible licensed individual is.
2. Look up the number. DLI’s Choosing a plumber page links to its lookup as “Check a plumber’s license here.”
3. Check the expiration date.
4. Ask each worker for a license or registration. DLI says plumbers should carry their license at all times on a work site.

For the general steps, see how to check a contractor’s license.

How to file a plumbing complaint

DLI licenses and regulates all plumbing work in Minnesota. It investigates complaints to decide whether plumbing laws were broken.

1. File. Create an iMS account and file online, or download the complaint form. Consumers, business owners, other plumbers and inspectors can file.
2. Response. DLI usually sends the complaint to the plumber and asks for a written response. It then sends you a copy of that response.
3. Enforcement. When DLI proves a violation, it can impose fines, suspend or revoke a license, or invoke the plumber’s bond to correct non-complying work. DLI cites Minnesota Statutes 144.989 to 144.993. You can view enforcement actions against licensees.

DLI says it cannot require a plumber to resolve a dispute, pay damages or correct work unless it finds Minnesota Plumbing Code violations. Some disputes must go to court. For money problems, see our guide to contractor problems. The complaint page gives no phone number. DLI’s Choosing a plumber page gives 651-284-5067 for questions.

Questions to ask before you hire

• What is your plumbing contractor license number, and when does it expire?
• Who is your responsible licensed individual? Is that person a master plumber?
• If your license is restricted, what bond and insurance do you carry?
• Can I see your insurance certificate?
• Is each person doing the work licensed or registered, and is a licensed plumber on site to supervise?
• Who will pull the permit, and who will schedule the inspection?

If your project is in Duluth, MN, our guide to building permits in Duluth, MN covers which home work, including plumbing, needs a permit there and who should pull it.

Common questions

Sources

Every rule, number and deadline in this guide comes from these official pages, read on November 12, 2026. Rules change. The source is always the final word.

• Choosing a plumber (Minnesota Department of Labor and Industry)
• Plumbing contractor licensing basics (Minnesota Department of Labor and Industry)
• Plumbing license types and credentials (Minnesota Department of Labor and Industry)
• Plumbing complaints (Minnesota Department of Labor and Industry)
• Plumbing (Minnesota Department of Labor and Industry)
• Plumbing inspections (Minnesota Department of Labor and Industry)

This guide is general information, not legal advice.