| Alabama | Alabama Plumbers & Gas Fitters Examining Board ↗ | Guide |
| Alaska | Alaska Department of Labor, Mechanical Inspection ↗ | Guide |
| Arizona | Arizona Registrar of Contractors ↗ | Guide |
| Arkansas | Arkansas Department of Health, Plumbing and Natural Gas ↗ | Guide |
| California | Contractors State License Board (C-36) ↗ | Guide |
| Colorado | Colorado Examining Board of Plumbers (DORA) ↗ | Guide |
| Connecticut | Connecticut Department of Consumer Protection ↗ | Guide |
| Delaware | Delaware Board of Plumbing, Heating, Ventilation, Air Conditioning and Refrigeration Examiners ↗ | Guide |
| District of Columbia | DC Department of Licensing and Consumer Protection ↗ | Guide |
| Florida | Florida Construction Industry Licensing Board (DBPR) ↗ | Guide |
| Georgia | Georgia State Construction Industry Licensing Board ↗ | Guide |
| Hawaii | Hawaii Board of Electricians and Plumbers ↗ | Guide |
| Idaho | Idaho Division of Occupational and Professional Licenses ↗ | Guide |
| Illinois | Illinois Department of Public Health (plumbing) ↗ | Guide |
| Indiana | Indiana Plumbing Commission (Professional Licensing Agency) ↗ | Guide |
| Iowa | Iowa Plumbing and Mechanical Systems Board ↗ | Guide |
| Kansas | No statewide license in Kansas for this work. Your city or county licenses it. | Guide |
| Kentucky | Kentucky Department of Housing, Buildings and Construction ↗ | Guide |
| Louisiana | Louisiana State Plumbing Board ↗ | Guide |
| Maine | Maine Plumbers' Examining Board ↗ | Guide |
| Maryland | Maryland State Board of Plumbing ↗ | Guide |
| Massachusetts | Massachusetts Board of State Examiners of Plumbers and Gas Fitters ↗ | Guide |
| Michigan | Michigan LARA Bureau of Construction Codes ↗ | Guide |
| Minnesota | Minnesota Department of Labor and Industry ↗ | Guide |
| Mississippi | Mississippi State Board of Contractors ↗ | Guide |
| Missouri | No statewide license in Missouri for this work. Your city or county licenses it. | Guide |
| Montana | Montana Board of Plumbers ↗ | Guide |
| Nebraska | No statewide license in Nebraska for this work. Your city or county licenses it. | Guide |
| Nevada | Nevada State Contractors Board ↗ | Guide |
| New Hampshire | New Hampshire Mechanical Licensing Board (OPLC) ↗ | Guide |
| New Jersey | New Jersey State Board of Master Plumbers ↗ | Guide |
| New Mexico | New Mexico Construction Industries Division ↗ | Guide |
| New York | No statewide license in New York for this work. Your city or county licenses it. | Guide |
| North Carolina | North Carolina State Board of Examiners of Plumbing, Heating and Fire Sprinkler Contractors ↗ | Guide |
| North Dakota | North Dakota State Plumbing Board | Guide |
| Ohio | Ohio Construction Industry Licensing Board ↗ | Guide |
| Oklahoma | Oklahoma Construction Industries Board ↗ | Guide |
| Oregon | Oregon Building Codes Division + CCB ↗ | Guide |
| Pennsylvania | No statewide license in Pennsylvania for this work. Your city or county licenses it. | Guide |
| Rhode Island | Rhode Island Department of Labor and Training ↗ | Guide |
| South Carolina | South Carolina LLR ↗ | Guide |
| South Dakota | South Dakota State Plumbing Commission ↗ | Guide |
| Tennessee | Tennessee Board for Licensing Contractors ↗ | Guide |
| Texas | Texas State Board of Plumbing Examiners ↗ | Guide |
| Utah | Utah Division of Professional Licensing ↗ | Guide |
| Vermont | Vermont Division of Fire Safety (plumbing licensing) ↗ | Guide |
| Virginia | Virginia Board for Contractors (DPOR) ↗ | Guide |
| Washington | Washington Department of Labor and Industries ↗ | Guide |
| West Virginia | West Virginia State Fire Marshal ↗ | Guide |
| Wisconsin | Wisconsin Department of Safety and Professional Services ↗ | Guide |
| Wyoming | No statewide license in Wyoming for this work. Your city or county licenses it. | Guide |