Glossary

A USDOT number is the ID the Federal Motor Carrier Safety Administration (FMCSA) gives a company that runs commercial vehicles. A company hauling cargo between states must have one, and some states require one for trucks that stay inside the state. FMCSA uses it to keep the company's safety record from audits, inspections and crash reports.¹ Listings built from the registry show the number and link to its record.

In FMCSA's rules, interstate commerce is transportation between a place in one state and a place outside it. Intrastate commerce is everything else.² An intrastate carrier works entirely within one state, on trips that don't start or end in another state or country.³ A company's SAFER record shows which it registered as, under Carrier Operation.⁴

Power units are the vehicles a carrier owns, trip-leases or term-leases, as FMCSA counts them.³ A contractor reports the number on its registration, and the fleet size on this site's listings comes from it.

Maine defines a master plumber as a licensed person in, or about to go into, the business of installing plumbing. The license takes a year as a licensed journeyman, or four years as a licensed trainee under a master plumber.⁵ Delaware's plumbing code holds the master plumber responsible for all the work done under a plumbing permit.⁶

In Maine a journeyman plumber installs plumbing and drainage while employed and directed by a master plumber, or does plumbing repair as a regular part-time job without being a master. The license takes two years as a licensed trainee under a master plumber, or 2,000 hours as a journeyman-in-training.⁵

Iowa counts as a contractor any person or business that provides plumbing, mechanical, HVAC, refrigeration, sheet metal or hydronic services under contract. Every plumbing and mechanical contractor there needs a license from the state's board and a state contractor registration, and the business must hold or employ someone with an active master license, carry at least $500,000 of liability insurance and post a $5,000 surety bond.⁷ South Carolina's plumbing classification covers installing, replacing, altering and repairing plumbing on a property, including water supply piping, fixtures and appliances and the drain and vent systems.⁸

South Carolina law defines a mechanical contractor as a business that performs or supervises mechanical construction, or offers to. Its classifications include air conditioning, heating, packaged equipment, plumbing and refrigeration, and mechanical work costing more than $10,000 needs a license.⁸ In Minnesota a business has to file a $25,000 mechanical contractor bond with the state before it contracts for gas, heating, ventilation, cooling, air conditioning, fuel burning or refrigeration work.⁹

HVACR, also written HVAC/R, stands for heating, ventilation, air conditioning and refrigeration. Arkansas tests HVAC/R contractors and issues their licenses.¹⁰ Maryland's HVACR board licenses the people who provide HVACR services to homes and businesses.¹¹

A backflow prevention assembly keeps contaminated water from getting into a public water system's drinking water pipes, and Missouri requires every one to be inspected and tested by a certified tester.¹² Reduced pressure assemblies and double check valve assemblies are among the types Washington approves, and they're tested when they're installed, repaired or moved and every year after that.¹³ Minnesota's plumbing code has a certified backflow assembly tester do the test and tag the assembly with the date, a signature and the tester's certification number.¹⁴

The Uniform Plumbing Code (UPC) is a plumbing code published by the International Association of Plumbing and Mechanical Officials (IAPMO). Minnesota's plumbing code is built on the 2018 edition with the state's amendments,¹⁴ and Nevada's State Public Works Board adopts the 2024 edition for the state's own buildings.¹⁵

The International Plumbing Code (IPC) is a plumbing code published by the International Code Council (ICC). Michigan's plumbing rules adopt the 2021 edition.¹⁶ Delaware adopts the 2021 edition with its own amendments, and every county, city and town there enforces it.⁶

The International Mechanical Code (IMC) is a mechanical code published by the International Code Council. Minnesota's mechanical code takes in chapters 2 to 15 of the 2018 edition,¹⁷ and Michigan's mechanical rules adopt the 2021 edition.¹⁸

The Uniform Mechanical Code (UMC) is a mechanical code published by the International Association of Plumbing and Mechanical Officials. Nevada's State Public Works Board adopts the 2024 edition for the state's own buildings, and in the building and residential codes it adopts, it replaces references to the International Plumbing Code and International Mechanical Code with the Uniform Plumbing Code and Uniform Mechanical Code.¹⁵

C-36 is the Plumbing Contractor classification of California's Contractors State License Board (CSLB).¹⁹ CSLB licenses and regulates the state's construction industry.²⁰

C-20 is CSLB's Warm-Air Heating, Ventilating and Air-Conditioning Contractor classification in California.¹⁹