Colorado plumbing license and your Denver Plumbing A license: what they let you do and your first 30 days

Published November 3, 2026 · Colorado Revised Statutes 2026, the State Plumbing Board's rules (in effect since August 14, 2026) and pages, the 2025 Denver Building Code, Denver Water's backflow rules and Xcel's gas meter rules checked November 3, 2026

• Free. The printable checklist comes by email. The full checklist and the job table are on this page too, nothing held back.
• Deepsel is our product: free estimate, invoice and scheduling software for contractors (scheduling and dispatch, quotes, invoicing, card payments). The section before the FAQ says where it fits and where it doesn't.
• Not legal advice. Every rule links to the statute, board rule, code section or agency page it comes from. Ask the State Plumbing Board, Denver Contractor Licensing or a Colorado attorney before you bet a job on my reading.

Colorado licenses the plumber and registers the company. Denver adds its own Plumbing A license on top. Your state plumbing contractor registration lets the company plan, install and repair plumbing for other people anywhere in Colorado, at any job size, as long as a full-time master plumber is responsible for all of it. Denver's Plumbing A license lets you pull Denver permits for drains, water piping, storm sewer, gas piping, water heaters, gas ranges and pool piping, and Denver inspects that work itself.^{1, 10} Four dates run your first months: your registration number and your master's license number have had to be on your trucks, bids, invoices and website since July 1, 2025; apprentices get registered within 30 days of hire; the current cycle of Colorado plumbing licenses and contractor registrations ends February 28, 2027; and Denver's license renews every 2 years.^{1, 4, 11}

"In my state you are required to hold a master's license to open a legit business," a one-man plumbing company owner wrote on Reddit. In Colorado that's half right. The company needs a master, but the owner doesn't have to be one, and the master can stand behind one company only. The guides that rank for "Colorado plumbing license" stop at the exam. This page picks up after it, for a shop working in Denver: what each license covers, where it stops, the gray areas (gas, water heaters, backflow, drain cleaning), the permit and utility steps, a job-by-job table and a checklist for the first 30 days. If you also do remodeling or general building work, Denver's construction classes are in the Colorado contractor license article, the paperwork side is in what your Colorado contract must include, and the electrician's version of this page is the Colorado electrical license article.

The checklist also comes as a printable sheet with blanks for your registration, license, permit, policy and tester numbers and your renewal dates. Get it three ways: make your own copy in Google Docs (lands in your Drive), download the Word version (.docx), or download the PDF. Pick a format, enter your email and I'll send the links.

Colorado plumbing license classes and what each one lets you do

Colorado has three plumber licenses for people and one registration for the business. The license says what a person may do with their hands. The registration says the company may sell plumbing to other people.^{1, 4}

Sources for the table: the statute's definitions and requirements,¹ the board's rules and pages,^{3, 4} its licensing guide,⁵ Denver's licensing pages.^{10, 11}

Your Colorado plumbing contractor registration and the master behind it

The business and the license are separate things in Colorado. To act as a plumbing contractor, the company must "either be, or employ full-time, a master plumber, who shall be in charge of the supervision of all plumbing work performed by the contractor."¹ The owner can be a non-plumber. The master carries the weight: "A master plumber shall not be responsible for more than one plumbing contractor at a time," and "The master plumber is responsible for all plumbing work performed by the plumbing contractor."¹ Both the master and the owner sign the board's Acknowledgment of Responsibility, where the master affirms "I am actively engaged in a full time capacity, and I assume responsibility for all Plumbing work performed by the above-named Plumbing Contractor." The form also asks whether the master is already listed for a different company.⁶

If the master leaves, the clock is short. The master tells the board within 15 days.¹ The company gets 20 days to hire another master, after which its registration goes into a "Need Master Hire-Cannot Practice" status.³ There's one bridge: the board can issue a temporary master permit to finish a current project, but only if the company has a journeyworker on full time, and it lasts until the next scheduled exam.¹ A one-master shop should know who it would call before that day comes.

What the registration doesn't ask for is worth knowing too. On insurance, the statute, the board's rules and its online application ask only for workers' compensation and unemployment insurance information if you employ people. No bond, no liability certificate.^{1, 3, 6} The board's own Plumbing Licensing Guide says something different. It tells business owners they "will need to register as a plumbing contractor and carry specific insurance, including: Property Damage Insurance (minimum $100,000) General Liability Coverage (minimum $300,000)."⁵ I couldn't find that in the law. Carry at least that much anyway; general contractors and some cities will ask for more (more below).

If you're asked to be someone else's master

Plenty of new masters get asked to put their license behind another company. The legal floor is above: one company at a time, full time, and responsible for all of that company's plumbing. A master who isn't a registered contractor and works as an independent contractor for another business can't pull permits for it.¹ "Selling or fraudulently obtaining or furnishing a license or registration" is grounds for discipline, and Denver can suspend or revoke for "Allowing one's license or certificate to be used by another person."^{1, 9} A Colorado plumbing company owner described what happens anyway: "Most hire a master plumber in name only to pull permits. I turn them in to the state all the time" (Reddit). What the job pays and what it can cost you is a topic of its own. For scale, the federal Bureau of Labor Statistics puts the Colorado median for plumbers at $30.40 an hour in May 2025.³² The short version: your name is on every job they do.

Your Denver Plumbing A license on top

Denver's code says "Electrical and plumbing contractors must register with the Agency," and its license policy spells out what your registration covers: "To install, add to, alter or repair sanitary plumbing, potable water supply piping and appliances connected thereto, storm sewer, gas piping, water heaters, gas ranges, domestic gas incinerators, swimming pool and spa piping, solar plumbing utilized for potable water, and all medical gas and vacuum systems in health care facilities." All of it is done under the supervision of a state master plumber.^{9, 10} Plumbing A is Denver's only plumbing registration. There is no B or residential version. State law lets cities license plumbing contractors but bars them from rules that would keep a state licensee from practicing the trade.¹

To get it, you upload your current State of Colorado Plumbing Contractor card, a photocopy of the master's driver's license or ID, and your Secretary of State documents, and wait about 14 to 20 business days. The fee is $160, and it renews every 2 years, unlike Denver's 3-year construction and electrical licenses.^{9, 11} After that, Denver adds paperwork more than skills:

• Change of name or address goes to Contractor Licensing within 15 days. A change of legal entity, say from sole proprietor to LLC, needs a new license within 30 days.¹¹
• Renewal opens 30 days before expiry and runs to a year after it, but "No work shall commence or continue after the date of expiration."^{9, 11}
• You must "hire licensed subcontractors for those trades that require a City and County of Denver license."⁹

Other Denver licenses touch the same pipes, and it helps to know who holds them when you sub work out or get subbed:

Sources: Denver's license policy,¹⁰ quick permit lists,¹² fee table,¹¹ and the Denver Fire Department's licensing page.²⁰

Apprentices, journeyworkers and who can work alone

A licensed master, journeyworker or residential plumber can work alone, the residential plumber only on one- to four-family homes. An apprentice never can. "One licensed journeyworker plumber, master plumber, or residential plumber shall not supervise more than three plumbing apprentices at the same job site."¹ The board's rule defines direct supervision as the licensed plumber being "physically present at the same physical addresses listed on the permits and where the apprentice is working or no more than five minutes distance from the apprentice within the same construction or job site."³ The statute's annotation sums up a 2020 Court of Appeals case: supervision doesn't require line of sight, only being close enough "to monitor, inspect, and sign off on the apprentice's work with reasonable frequency."¹ One Colorado owner remembered it as "within 5 minutes or 5 miles" (Reddit). The rule says five minutes, on the same site. Drop the miles.

The paperwork around apprentices is where new contractors get letters from the board:

• Register each apprentice within 30 days of hire, and take them off your registration within 30 days of them leaving.^{1, 3} A first late registration gets a confidential letter of concern, a second a public letter of admonition.⁷
• By July 1 each year, report each apprentice's name and total training hours to the board.¹
• Keep records of each apprentice's dates and residential and commercial hours. You'll sign their experience forms later.³
• A residential plumber you send to a commercial job has to be registered as an apprentice and supervised there.³

The board sends its own people to check licenses and the apprentice ratio on job sites across the state, whoever issued the permit, and inspectors are required to review who did the work as part of their inspections.¹

Gas, water heaters, backflow and the other gray areas

The statute defines plumbing as the water piping, fixtures, traps, drains and vents inside a building or within five feet of its foundation, plus water conditioning appliances, multipurpose residential fire sprinklers, and medical gas and vacuum systems in health care buildings.¹ The edges are where new owners get stuck. Here is where each one lands:

• Gas piping. The statute's definition of plumbing leaves fuel gas out and defines gas piping separately, and the state's gas piping permit form lets a "Gas Pipe Installer" apply as well as a plumbing contractor or homeowner.^{1, 8} That's why HVAC and gas service contractors run gas too. For you it doesn't matter much: gas piping is in Denver's Plumbing A, and in areas the state inspects your master is a qualified applicant for gas piping permits.^{1, 10} Swapping a gas appliance onto an existing connection isn't gas piping under the statute's definition.¹
• Water heaters, gas and electric. The statute's exemption list mentions "water heating appliances," which reads like a loophole. The board's rule closes it: water heaters supplying domestic hot water "are not equipped with backflow preventers. Therefore, they do not fall under the exemption."³ Water heaters are licensed plumbing work, and they're named in your Denver license.¹⁰ Venting domestic water heaters is also listed under Denver's Gas Service license, so gas service contractors compete for the same swaps.¹⁰
• Backflow testing. A separate certificate. "Individuals who are engaged in inspecting, testing, or repairing backflow prevention devices are exempt from licensure," while installing or removing them is licensed plumbing work.¹ Testers need an ABPA or ASSE backflow prevention assembly tester certification.³ Details in the utility section below.
• Drain and sewer cleaning. The statute needs no license, registration or permit for "the repair, maintenance, and replacement of sinks, faucets, drains, showers, tubs, and toilets," or for disposals and dishwashers.¹ My reading: clearing a stoppage is open to non-plumbers, so a drain-cleaning company is your competitor without a license. Replacing a building drain or sewer pipe is plumbing.
• Water treatment. Softeners and filters connected to the water system are plumbing, and you can do them without the separate water conditioning registration.¹ Denver lists water softeners on its plumbing quick permits.¹²
• Fire sprinklers. Only the multipurpose kind, where the sprinkler piping is part of the cold water system in a one- or two-family home or townhouse, counts as plumbing.^{1, 3} Other sprinkler systems belong to fire suppression contractors registered with the state's Division of Fire Prevention and Control, and in Denver the installer also needs a Denver Fire Department license and Denver's Fire Protection Class B license.^{10, 20} The Fire Department licenses every sprinkler installer, so ask it before you quote even a multipurpose system in Denver.
• Septic. On-site wastewater systems inside the property line are excluded from the definition of plumbing.¹ They fall under the state's separate on-site wastewater law instead.
• Medical gas. Inside the definition and inside your Denver license.^{1, 10} It isn't a first-month job, and this page doesn't cover it.
• Well pumps. A plumber who installs or repairs well pumping equipment, up to and including the pressure tank, needs a license from the Water Well Construction and Pump Installation Contractors Board first.³

Where your Colorado plumbing license stops

• Heating and cooling. Building heating appliances and systems and air conditioning are outside the plumbing law.¹ Denver licenses that work through its heating, hot water, steam and refrigeration classes, so a boiler, furnace or hydronic system needs one of those.¹⁰ You can run the gas line to the furnace or boiler under your Plumbing A; the mechanical contractor sets the equipment under its own permit.
• Electrical. Colorado's electrical law lets "any vendor of any electrical appliance" sell, deliver and connect it "if the connection of the appliance does not necessitate the installation of electrical wiring of the structure," and plugging into an existing approved outlet isn't installing.³¹ So when you sell the water heater and the circuit is already there, the reconnection is yours, and so is a sump pump plugged into an outlet that's already there. A new circuit, a bigger breaker, a new outlet for a sump pump or a tankless heater, or a new circuit for a heat pump water heater is an electrician's job under an electrical permit.
• Walls and structure. Moving walls or framing for a bathroom remodel is building work. Denver's construction classes are in the Colorado contractor license article.
• Lead paint. Colorado doesn't run its own renovation program, so EPA's rule applies directly. Open more than 6 square feet of painted surface in a room (20 outside) in a home built before 1978 and the firm needs EPA lead-safe certification, which covers "all firms, even sole proprietorships."³⁰
• The street. Sewer work in the public right-of-way needs Denver's right-of-way permits, and Denver issues a separate right-of-way Sewer Contractor license.^{11, 14} Denver Water sets the water meter, not you.^{10, 17}

Colorado plumbing permit and code: who pulls it and who inspects

Only a "qualified applicant" may apply for a plumbing or gas piping permit from the state: a master plumber who is also a registered plumbing contractor, a master directly employed by one, or a homeowner working on their own home.¹ Permits are issued "in the name of the qualified applicant or registered contractor performing the work prior to the commencement of any work."³ Denver issues permits to licensed or registered contractors and to owner-occupiers with homeowner permits.⁹

Denver inspects its own plumbing. The state doesn't inspect inside Denver, or in the other local inspection areas on its list, which include Adams (except Federal Heights), Arapahoe (except Bow Mar and Sheridan), Boulder, Broomfield, Douglas, El Paso, Jefferson, Larimer and Weld counties, among 29 entries.⁸ Everywhere else, you buy a state permit online before work starts, and a state inspector comes within three working days of the request.^{1, 8}

Most house jobs in Denver are quick permits, issued online without plan review on a single-family home or duplex. The plumbing list: backflow preventers, dishwashers, floor drains, garbage disposals, gas piping outlets, showers, tubs and sinks, pool piping, washers, toilets, water heaters, water service and water softeners.¹² On new houses and additions, Denver now wants the issued Residential Construction Permit number before it issues your trade permit, so the builder's permit comes first.¹²

The water heater swap

It's the job this trade prices and argues about most. A Colorado husband-and-wife plumbing company listed what goes into theirs: "Everything is: 1)water heater ... 2)expansion tank and all the fittings and strap 3)new water valve for water heater if needed 4)pan ... 5) gas flex ... 6) water connections 7) new AGA gas valve 8) sediment trap 9) T&P extension 10) permit 11) licensing fee (in CO where we work you have to be licensed in every city to pull permits ...)." Their price for all of it "is always less than $2000 on a normal atmospheric (40-50 gallon)" (Reddit, January 2025), and they put permits at "$100-$300 per jurisdiction" (Reddit). That's one company's statement, not a market price. The permit rules behind it:

• Denver, house or duplex: a quick permit (water heaters appear on both the plumbing and the mechanical lists).¹²
• Denver, apartments and commercial: since March 1, 2023 a gas-fired water heater can't go on a quick permit. You file a Building Log application with either an electrification feasibility report or gas leak testing of all the piping connected to the meter.¹²
• Emergencies: in Denver, the double fee for starting without a permit doesn't apply to emergency work if you apply within 3 working days.⁹ Where the state inspects, its code lets you get the permit "the following business day" for a water heater replacement or a broken line.³
• The state code's breaks for replacements: a new heater doesn't need a drain pan where the old one never required one, and the relief valve discharge doesn't have to be piped to a drain on a replacement.³ Check Denver's inspector before relying on either inside Denver.

Three permit rules catch new contractors:

• Pull your own. Never work under the homeowner's or the last contractor's permit. The same owner again: "I also don't like to pull permits on jobs I didn't do all the work on, as I don't want to become responsible for someone else's work" (Reddit).
• Permit before work. Denver doubles the permit fee (at least $100) for work started without one and adds an investigation fee of the same amount.⁹ The state doubles its fee too, and the board's fine for a missing permit or inspection is $375, then $900.³
• The homeowner exemption is the owner's. Colorado lets people plumb their own home, but not one built to sell, a rental or a commercial building.¹ Denver's homeowner permits are for owner-occupied single-family homes only, after an exam, and "A licensed Denver contractor may not serve as a designated worker."^{9, 13}

The Colorado plumbing code

The state's code is the 2024 International Plumbing Code and the plumbing chapters of the 2024 International Residential Code, with the board's amendments, and gas follows the Colorado Fuel Gas Code, built on the 2024 International Fuel Gas Code. The board's current rules took effect August 14, 2026.³ Towns may adopt stricter codes.¹ Denver did: the 2025 Denver Plumbing Code is its own set of amendments to the 2024 International Plumbing Code, and Denver's administration chapter replaces the model code's permit sections.⁹

Outside Denver

Cities can license plumbing contractors, but the contractor still registers with the state, and no city can keep a state licensee from practicing the trade.¹ They differ on paperwork and insurance:

Anywhere else, call the building department before you quote and ask three things: do you license or register plumbing contractors, what insurance certificate do you want, and who inspects. The Colorado owner quoted above put it as "you have to be licensed in every city to pull permits." Aurora is the easy one: it only wants your state cards on file.

Denver Water, backflow and Xcel gas meters

Denver Water

Denver Water requires an approved backflow prevention assembly on every commercial, industrial, irrigation and fire line service, and on homes depending on the hazard, "tested upon installation and annually thereafter by a certified backflow prevention assembly tester."¹⁷ If you take on testing:

• Get an ABPA or ASSE tester certification. Since March 2025 no plumbing license is needed to test, inspect or repair, and Denver Water says so on its program page. Assemblies on fire lines also need the state's "Fire Suppression System Contractor-Backflow" registration before Denver Water accepts the test.^{17, 18, 20}
• Send every test report to crossconnectioncontrol@denverwater.org with "Backflow Test Reports" in the subject line, and report a failed test "within 24 hours of failure at (303) 628-5969."¹⁷
• Tag the device. Since July 1, 2025, a licensed plumber who installs, tests, inspects, repairs or reinstalls a backflow preventer must attach a tag with the business name and contact, the contractor registration or master license number, the date and what was done.¹
• Tests run at installation, after a repair or move, and at least once a year, using the procedure of the certifying body.³ Irrigation assemblies get tested as the water comes on, in a May to September season, and Denver Water mails owners a reminder 30 days before a test is due. Owners who ignore three notices get a $250 charge and a service suspension.¹⁷

Two more Denver Water rules land on remodels and new work. Before Denver issues a building permit for a major renovation, addition or remodel of a house or a single-structure apartment building, Denver Water evaluates the water service line, and an old or non-copper line may have to be replaced. And Denver Water makes the tap and sets the meter: you install the service line, stop box and meter pit to its standards, and it inspects the pit within three business days before setting the meter.¹⁷ Other water districts around the metro run their own programs. Ask each one how it wants backflow reports.

Xcel Energy gas

Denver is Xcel Energy territory for gas. "The meter may be set if an approved city or county inspection has been received," and "For all gas meters, only Xcel Energy may unlock or operate the inlet valve." Authorized heating contractors and gas inspectors may operate the outlet valve only after the installation passes.¹⁹ Where the state inspects, the approval is a "Blue Tag" on the piping at the utility connection.³ Questions about a new meter or a bigger one for a tankless heater or generator go to Xcel's Builders Call Line, 800-628-2121.¹⁹

Can I take this job? A table for Denver plumbing contractors

The verdicts assume you hold a state plumbing contractor registration with a responsible master and a Denver Plumbing A license, and the job is a single-family home or duplex in Denver. "Sub it out" means another licensed contractor pulls its own permit for that part.

Your first 30 days: the checklist

This is the whole checklist. The printable version is the same list laid out to tick off, with blanks for the numbers.

A. Licenses and registrations, week 1

1. Look up the company's plumbing contractor registration and the master's license on the DORA license lookup and write down both expiration dates. Every Colorado plumbing license and contractor registration expires on the last day of February in odd-numbered years, so most read February 28, 2027 (one issued within 120 days of that date gets the next one). Renewal opens about 4 to 5 weeks before, there's a 60-day grace period with a late fee, and from March 1, 2027 licenses run three years.^{1, 3, 4} Close out old permits before then: the board won't renew a contractor registration "with expired permits" until they're cleared.³
2. Look up your Denver Plumbing A license on Denver's licensee search and add it to your e-permits account. It renews every 2 years, from 30 days before the date on the license to a year after, with no work in between.^{9, 11}
3. Confirm the responsible master signed the Acknowledgment of Responsibility with the owner, works full time for you and is named for no other company. If the master leaves: the master tells the board within 15 days, and you have 20 days to hire another.^{1, 3, 6}
4. Advertise only under your registered name. The board's rule: registered plumbing contractors "shall not advertise in any manner by any name, including DBA's, other than the registered company name on record."³ Report name, address, phone or email changes to the board within 30 days and name or address changes to Denver within 15; a new legal entity needs a new Denver license within 30 days.^{3, 11}
5. Every plumber carries their license and every apprentice their registration card on the job.^{3, 5}

B. Your numbers on trucks, bids, invoices and the website

Required since July 1, 2025: the plumbing contractor's registration number and the responsible master's license number, both, wherever the public sees you.^{1, 3, 4} The board's fine for missing them is $225, then $600.³

6. Vehicles: every company vehicle, and any personal vehicle used for the business, shows both numbers in at least two places, in lettering at least two inches high.
7. Bids: on every bid form, at the top of the first page or on the cover page. When you bid through a general contractor, write them on the GC's bid form or on your own cover sheet.
8. Invoices and receipts: both numbers near your contact information.
9. Website: prominently on the home page, and on the contact and about pages. Social media pages that advertise the business too.
10. If either number changes (a new master, say), update every display within 90 days.

C. Insurance, workers' comp, taxes and apprentices

11. Workers' compensation. With one or more employees, "you must have workers' compensation insurance," part-time and family members included. With none, a construction contractor needs a policy or a filed rejection of coverage, and general contractors will ask for proof.²⁵ The state registration asks for your certificate if you employ anyone.⁶
12. Open an unemployment insurance account with the Colorado Department of Labor and Employment if you employ people. The registration asks for the account details.^{1, 6}
13. General liability. No minimum in the statute or the board's rules; the board's guide lists $300,000 general liability and $100,000 property damage. Denver, Boulder and the Pikes Peak Regional Building Department want $1,000,000 per occurrence and $2,000,000 aggregate.^{5, 10, 22, 23}
14. Bond: none required by the state or Denver.^{1, 6, 11}
15. Denver Treasury. Denver's Occupational Privilege Tax is $4 a month for each owner or manager working in Denver and $9.75 a month for each employee who earns $500 or more there in a month ($5.75 of it withheld from the employee). It applies "regardless of whether a permanent location is maintained in Denver." Denver also charges use tax on materials and tools used on Denver jobs when no Denver sales tax was paid, and "does not collect use tax at the time a building permit is issued," so open a consumer use tax account too.¹⁶
16. Register each apprentice within 30 days of hire, keep to three per licensed plumber on a job site, report their hours by July 1, and take them off your registration within 30 days of them leaving.^{1, 3}

D. The cities you'll work in

17. Aurora: file your state master's and contractor's licenses with the Building Division.²¹
18. Colorado Springs and El Paso County: register with the Pikes Peak Regional Building Department, insurance certificate first.²²
19. Boulder: get the City of Boulder plumbing contractor license.²³
20. Fort Collins: register your master plumber and get a city business license.²⁴
21. Set up the state's online permit account if you'll work where the state inspects.⁸ For any other town, call the building department before you quote.

E. Utilities

22. Denver Water: save crossconnectioncontrol@denverwater.org and 303-628-5969 if you'll test backflow; on remodels and additions, ask whether the service line evaluation is done before you price the job.¹⁷
23. Xcel Energy: save the Builders Call Line, 800-628-2121. Gas meters are set only after an approved inspection, and only Xcel operates the inlet valve.¹⁹
24. Other water districts in your area: ask how they want backflow reports and who sets meters.

F. Paperwork, quotes and jobs

25. Put a permit line on every quote that needs one, and pull every permit in your own name, with the master as applicant.^{1, 3}
26. Carry backflow tags and fill one in on every device you install, test or repair.¹
27. If you'll test backflow, get the ABPA or ASSE tester certification and keep your test kit calibration current.^{3, 17}
28. If you'll open pre-1978 walls, get the firm EPA lead-safe certified and a certified renovator on the crew.³⁰
29. Line up the subs you'll need: an electrician, an HVAC or hot water contractor, a fire sprinkler contractor, a well pump contractor if you work outside the city, and a building contractor for remodels that move walls.

G. Renewal and continuing education

30. Put every renewal in the calendar with a 60-day reminder: state registration and each plumber's license (February 28, 2027 for most), Denver license (2 years), insurance, workers' comp, city licenses, tester certification.
31. Continuing education: each licensed plumber needs 8 hours for each license year (March 1 to February 28) since the last renewal, at least 4 hours on codes in every 24 months and no more than 2 on safety, from a provider on the board's attested list. At renewal you also attest that you've read the current Colorado Plumbing Code. The first renewal after passing the exam is exempt.^{1, 3, 4}

What happens if you cross the line

Working without a license, a registration or a permit

• It can be a crime. Working at the trade of a residential, journeyworker, master or apprentice plumber "without an active license, permit, or registration" is a class 2 misdemeanor: up to 120 days in jail, a fine of up to $750, or both.²
• Board fines. Up to $1,000 for a first offense, $2,000 for a second and $2,000 a day after that.¹ The board's schedule: operating as a plumbing contractor without registration $750, then $1,500; employing unlicensed people to do plumbing $300, then $600; no permit or no inspection $375, then $900; applying for a permit when you aren't a qualified applicant $375, then $900; breaking the apprentice ratio $375, then $600; not displaying your numbers $225, then $600.³
• An expired license. Practicing on one is discipline too. The board's policy is a confidential letter of concern for 60 days to a year, a public letter of admonition for one to two years, and worse beyond that.⁷
• Denver's penalties. Breaking the building code carries the city's general penalty of up to $999, up to 300 days in jail, or both, and "each day an offense and violation continues shall constitute a separate offense." Work without a permit pays double fees plus an investigation fee, the violation notice can be recorded against the property, and Denver can suspend or revoke your license for up to three years.^{9, 15}
• The customer can sue. Failing "to obtain all governmental licenses or permits required to perform the services" is a deceptive trade practice under the Colorado Consumer Protection Act: actual damages or $500, whichever is more, three times damages for bad faith, plus attorney fees, and the state can seek up to $20,000 per violation ($50,000 when the customer is elderly).²⁶

Getting paid

One of Colorado's key cases on this is a plumbing case. In 1956 an unlicensed plumber sued a general contractor for $2,750 of plumbing and furnace work. The Colorado Supreme Court said "Contracts for services by one who is required by statute to have a license to engage in the particular profession, trade, or calling, and who does not have such a license are generally unenforcible." He could recover only for "the materials furnished and labor performed not requiring the services of a licensed plumber," which in his case meant the materials he supplied and the furnace installation, not the plumbing labor.²⁸ The Court of Appeals put it more bluntly in 1994: a contractor that needed licenses and permits and didn't get them "cannot recover compensation for its services."^{27, 29} An expired registration or an unpermitted job can cost you the invoice, not only a fine.

Insurance

I found no Colorado rule on what unlicensed or unpermitted work does to your own policy. The state's permit page warns homeowners that their insurance "may not cover the costs of repair for the work performed by anyone without liability insurance who causes damage to your home."⁸ Your policy wording decides your side, so ask your agent in writing whether you're covered for work done without a required permit, and keep the reply.

Lending your license

Masters get asked to "sign for" other companies. The statute lists "Selling or fraudulently obtaining or furnishing a license or registration" as grounds for discipline, Denver lists "Allowing one's license or certificate to be used by another person," and because the master "is responsible for all plumbing work performed by the plumbing contractor," the risk follows the name.^{1, 9} The supervisor of an apprentice is answerable for the apprentice's work too, and the board can act on the supervisor's license for it.¹

More for new plumbing contractors

• How much to charge per hour: service call minimum, first hour and flat prices, with a free rate sheet.
• Water heater replacement checklist: the code items, the permit and what to charge, with a free printable.
• You got your master plumber license. Now what? Stay for a raise or start your own plumbing business, with the numbers for each.
• Asked to be the master of record: what being a company's plumbing qualifier pays, and what it can cost you.

Where Deepsel fits

Deepsel is the field service software I build, and it doesn't know Colorado's plumbing rules. It won't pull a permit, track your license or CE dates, file a backflow report with Denver Water or letter your truck. It has no field for a license number either. Here's what it does help with. The invoice footer you set once is copied onto every invoice and prints just above your address and contact details, so your registration number and your master's license number land where the board wants them on billing. The shop-wide terms text is copied onto every quote under "Terms," below the line items. That puts both numbers on every quote, though not at the top of the first page, where the board's rule says they should appear; on a general contractor's bid package, add a cover sheet with them. And you can build a checklist template once in Settings (say: permit pulled, expansion tank, pan, sediment trap, T&P discharge, inspection passed) and add it to each water heater quote; it stays internal, and every tick records who checked it and when. Quotes can carry options, customers approve and sign on screen, and an optional card deposit is credited on the final invoice. Free covers 30 estimates and 30 invoices a month for your whole team; Pro is $29 a month with unlimited estimates and invoices (pricing). If you send invoices from a template today, the plumbing invoice template has a license number line in its From block; in Colorado, put both numbers there.

Frequently asked questions

Do plumbers need a license in Colorado?

Yes. Nobody may work at the trade of a residential, journeyworker or master plumber in Colorado without a state license, and a business that offers plumbing to others must register with the State Plumbing Board as a plumbing contractor. Apprentices need no license but must be registered within 30 days of hire and supervised. Working without a license is a class 2 misdemeanor. The exceptions are narrow: your own home (not one built to sell or rent), and repairing or replacing sinks, faucets, drains, showers, tubs, toilets, disposals and dishwashers. Water heaters and shower valves are not in that exception.

Is there a Colorado plumbing contractor license?

Colorado calls it a registration. The State Plumbing Board registers the business once it is, or employs full time, a master plumber who is responsible for all its plumbing work, and once it shows it complies with the workers' compensation and unemployment laws if it has employees. The individual licenses are separate: residential plumber, journeyworker plumber and master plumber. There is no dollar limit on the jobs a registered contractor can take.

How do I get a Denver plumbing contractor license?

Get the state plumbing contractor registration first. Then apply in Denver's e-permits system for the Plumbing A license, uploading your current State of Colorado Plumbing Contractor card, a copy of the master plumber's driver's license or ID, and the Secretary of State documents for your company. Denver reviews applications in about 14 to 20 business days. The Plumbing A license costs $160 and renews every 2 years.

Who can pull a plumbing permit in Colorado?

Only a qualified applicant: a licensed master plumber who is also a registered plumbing contractor, a master plumber directly employed by a registered plumbing contractor, or a homeowner working on their own home. A master who isn't registered and works as an independent contractor for another business can't apply. Journeyworker and residential plumbers can't pull permits. In Denver, permits go to licensed or registered contractors and to owner-occupiers of single-family homes with homeowner permits.

What is the apprentice ratio for plumbers in Colorado?

Three apprentices per licensed plumber at the same job site. The supervising master, journeyworker or residential plumber must be at the address on the permit where the apprentice is working, or no more than five minutes away on the same job site. The contractor registers each apprentice with the State Plumbing Board within 30 days of hiring them and reports their hours by July 1 each year. The board's fine for going over the ratio is $375 for a first offense and $600 for a second.

When do Colorado plumbing licenses expire, and how much continuing education do I need?

Every Colorado plumbing license and plumbing contractor registration expires on the last day of February in odd-numbered years, so the current ones expire February 28, 2027. Renewal opens about 4 to 5 weeks before, with a 60-day grace period and a late fee after. From March 1, 2027 licenses run three years. Each licensed plumber needs 8 hours of continuing education for each license year (March 1 to February 28), at least 4 of them on codes in every 24 months and no more than 2 on safety, except for the first renewal after passing the license exam.

Do I need a plumbing license to run gas lines in Colorado?

Colorado's plumbing law defines plumbing without fuel gas and defines gas piping separately, so the state license law doesn't make gas a plumbers-only trade. Gas piping still needs a permit and inspection under the Colorado Fuel Gas Code. In Denver, gas piping is part of the Plumbing A license, and Denver's Gas Service and HVAC licenses cover it too. In areas the state inspects, a registered plumbing contractor's master can pull the state gas piping permit.

Do I need insurance or a bond for a Colorado plumbing contractor registration?

The statute, the board's rules and the online application ask only for workers' compensation and unemployment insurance information if you have employees. There is no bond. The board's own Plumbing Licensing Guide says business owners should carry at least $300,000 general liability and $100,000 property damage insurance, which the law doesn't state, so I'd carry at least that. Some cities set more: Denver's licensing policy requires $1,000,000 per occurrence and $2,000,000 aggregate general liability for every Denver license and registration, plus workers' compensation of $100,000 per occurrence and $250,000 aggregate (or a rejection of coverage if you have no employees). Boulder and the Pikes Peak Regional Building Department also want $1,000,000 per occurrence and $2,000,000 aggregate.

Who can test backflow preventers in Colorado?

A certified cross-connection control technician: someone holding a backflow prevention assembly tester certification from ABPA or ASSE. Since March 2025 no plumbing license is needed to test, inspect or repair backflow preventers, but installing or removing one is licensed plumbing work. A licensed plumber who installs, tests or repairs a device must tag it with the business, the registration or master license number, the date and the service. Denver Water wants test reports by email and failed tests reported within 24 hours.

How much does a licensed plumber make in Colorado?

The federal Bureau of Labor Statistics puts the May 2025 median for plumbers, pipefitters and steamfitters in Colorado at $30.40 an hour, or $63,240 a year, and $30.72 an hour in the Denver-Aurora-Centennial metro area. That is employee pay and includes pipefitters, so as a business owner treat it as the floor your own hour has to cover before overhead and profit.

What plumbing code does Colorado use?

The Colorado Plumbing Code: the 2024 International Plumbing Code and the plumbing chapters of the 2024 International Residential Code, with the State Plumbing Board's amendments. The current version of the board's rules took effect August 14, 2026. Gas follows the Colorado Fuel Gas Code, based on the 2024 International Fuel Gas Code. Towns can adopt stricter codes: Denver uses the 2025 Denver Plumbing Code, its own amendments to the 2024 International Plumbing Code.

Sources

1. Colorado Revised Statutes title 12, article 155 (plumbers): 12-155-103 (definitions: gas piping; journeyworker; master; plumbing, within the building or five feet of the foundation, including water conditioning appliances, multipurpose residential fire sprinklers and medical gas, excluding public water and sewer systems and on-site wastewater systems; apprentice; plumbing contractor; residential plumber; water conditioning), 12-155-106 (Colorado plumbing and fuel gas codes; local amendments), 12-155-108 (license required; apprentices registered within 30 days; contractor registration, workers' compensation and unemployment compliance, a full-time master for one contractor at a time, 15-day notice, responsible for all work), 12-155-109 (titles), 12-155-110 (experience), 12-155-112 (three-year licenses from March 1, 2027; continuing education), 12-155-113 (discipline, including false advertising, failure to supervise, employing unlicensed persons, selling or furnishing a license, permits by non-qualified applicants, display), 12-155-117(4) (temporary master permit), 12-155-118 (exemptions: own property; backflow testing; appliances, heating, air conditioning and fire protection; sinks, faucets, drains, showers, tubs, toilets, disposals and dishwashers), 12-155-119(5) (compliance checks), 12-155-120 (state inspection, three working days, qualified applicant, 12-month permits), 12-155-121 (local licensing), 12-155-122, 12-155-123 (fines up to $1,000, $2,000 and $2,000 per day), 12-155-124 (three apprentices per licensed plumber at the same job site; supervisor responsible; hours report by July 1; annotation to Welch v. Colorado State Plumbing Board, 2020 COA 130), 12-155-125 (display of registration and master license numbers from July 1, 2025), 12-155-126 (backflow device tags from July 1, 2025). olls.info, Colorado Revised Statutes 2026, read November 3, 2026.
2. C.R.S. 12-20-407(1)(a)(IV) (working at the trade of a residential, journeyworker, master or apprentice plumber without an active license, permit or registration is a class 2 misdemeanor), olls.info title 12; C.R.S. 18-1.3-501(1)(a.5) (class 2 misdemeanor: up to 120 days, up to $750, or both), olls.info title 18. Read November 3, 2026.
3. State Plumbing Board Rules and Regulations, 3 CCR 720-1, version effective August 14, 2026: rule 1.2(A) and (B) (Colorado Plumbing Code on the 2024 IPC and IRC; Colorado Fuel Gas Code on the 2024 IFGC), 1.2(D)(8) to (10) (certified cross-connection control technician: ABPA or ASSE; water heaters not exempt; shower valves are not faucets; backflow installation is licensed work), 1.2(E)(1) (emergency permits the next business day; direct supervision within five minutes; annual backflow testing; water heater replacement exceptions for relief valve discharge and pans), 1.3 (apprentices: residential plumbers on commercial jobs, 30-day registration and removal, records), 1.4(E) (60-day grace period, continuing education, no contractor renewal with expired permits), 1.4(F) (pumping equipment), 1.4(G) (carry licenses), 1.4(I) (20 days to replace a responsible master), 1.4(L) (changes within 30 days), 1.4(M) (advertising under the registered name), 1.4(N) (display on vehicles, bids, billing and websites), 1.6 (permits in the performer's name, double fee, inspections, Blue Tag), 1.7(D) (fine schedule). sos.state.co.us, read November 3, 2026.
4. Colorado State Plumbing Board: homepage (8 hours of CE each license year, March 1 to February 28), dpo.colorado.gov/Plumbing; "Applications and Forms" (experience; contractor registration with a responsible master for one company only; licenses and registrations expire on the final day of February of odd-numbered years; renewals open 4 to 5 weeks before; 120-day rule for new licenses), dpo.colorado.gov; "News" (display details; three-year licenses from March 1, 2027, next expiration in 2030), dpo.colorado.gov; "Colorado Plumbing CE," dpo.colorado.gov. All read November 3, 2026.
5. Colorado State Plumbing Board, "Plumbing Licensing Guide" (contractor requirements; insurance for business owners: property damage minimum $100,000, general liability minimum $300,000; apprentice registration fee $30; carry the registration card). PDF, read November 3, 2026.
6. Colorado State Plumbing Board, "Plumbing Contractor (PC) Application" preview (a master in charge of all plumbing; Acknowledgment of Responsibility; workers' compensation certificate and unemployment insurance information if you have employees), Google Docs; "Acknowledgment of Responsibility | Plumbing Contractor," PDF. Both read November 3, 2026.
7. Colorado State Plumbing Board, Policy Statements, October 29, 2025 (1.1 late apprentice registration; 2.3 practicing on an expired license). PDF, read November 3, 2026.
8. Colorado Division of Professions and Occupations, "Colorado Electrical and Plumbing Permits Homepage" (plumbing local inspection areas; homeowner notice; permit routes for plumbing contractors and fuel gas pipe installers), dpo.colorado.gov; "Gas Piping Permit Application" (applicants: plumbing contractor, homeowner, gas pipe installer; separate from the plumbing permit), PDF. Both read November 3, 2026.
9. City and County of Denver, 2025 Denver Building Code, Administration and the Denver Plumbing Code (2025 Denver amendments to the 2024 IPC): 107.3 and 107.4.1 (penalties under DRMC 1-13; recorded notice), 121.1 and 121.2 (registrants; "Electrical and plumbing contractors must register with the Agency"), 125.1 (plumbing registrations renewed every 2 years; no work after expiration), 125.3.3 (new legal entity), 126.1 and 126.2 (permits before work; licensed subcontractors; insurance "as defined by the building official in policy"; registrants follow the State Plumbing Board), 127.1 and 127.4 (discipline, including "Allowing one's license or certificate to be used by another person"; up to three years), 130.3.3 (no plumbing permit for like-for-like sinks, disposals and water closets in one- and two-family homes), 131.3 and 131.4 (who receives permits; homeowner permits; licensed contractors can't be designated workers), 138.2 and 138.3 (double fees, minimum $100, emergency exception within 3 working days; investigation fee). denvergov.org, read November 3, 2026.
10. Denver Community Planning and Development, building permit policy 25-DCBC 120A, "Classification of Licenses, Registrations and Certificates": Plumbing Registration Class A; Water service, Inside tap and backflow preventer and Drainlayer (Class D); Fire Protection Class B; Gas Service; Heating and Ventilating; HVAC Residential Only; Hot Water; Steam and Hot Water; Insurance Coverage Requirements, "for all scopes of work and licensure types": workers' compensation $100,000 per occurrence and $250,000 aggregate (or rejection of coverage with no employees), general liability $1M per occurrence and $2M aggregate. denvergov.org, read November 3, 2026.
11. City and County of Denver, Contractor Licensing: Contractor Licenses (renewal from 30 days before to one year after expiry), Apply for a Contractor's License (state plumbing contractor card and the master's ID; Secretary of State documents; 14 to 20 business days; right-of-way and sewer licenses apply separately), Contractor License Application (name or address change within 15 days; new legal entity within 30 days; no insurance or bond field), Contractor Licensing Fees (Plumbing A License, renewed every 2 years, $160; right-of-way Sewer Contractor, renewed annually, $50). All read November 3, 2026.
12. City and County of Denver, "Quick Permits": plumbing and mechanical lists for single-family and duplex homes; gas-fired water heaters in multifamily and commercial buildings; trade permits for new buildings and additions need an issued Residential Construction Permit; electrical exclusions for added equipment and connections. denvergov.org, read November 3, 2026.
13. City and County of Denver, "Applying for Permits as a Homeowner": single-family homes only; exam before plumbing work; the designated worker can't be paid. denvergov.org, read November 3, 2026.
14. City and County of Denver, Department of Transportation and Infrastructure, "Sewer Cut off and Repair and Pretreatment Devices Abandonment Entrance Requirements" (repairs by a licensed plumbing or sewer contractor; scheduling with DOTI; $55 per inspection). PDF, read November 3, 2026.
15. Denver Revised Municipal Code § 1-13, "General penalty": up to $999, up to 300 days, or both; each day a separate offense. library.municode.com, read November 3, 2026.
16. Denver Department of Finance, Treasury: Tax Guide Topic 61, "Occupational Privilege Taxes" ($5.75 employee and $4.00 business per month; owners, partners and managers; "regardless of whether a permanent location is maintained in Denver"), PDF; "General Contractors and Subcontractors - Construction within Denver" (use tax on construction materials, supplies, tools and equipment; not collected at the permit; consumer's use tax account), PDF. Both read November 3, 2026.
17. Denver Water, "Cross-Connection Control and Backflow Prevention Program" (assemblies required, annual tests by certified testers, reports to Cross Connection Control, HB25-1077, fire assemblies, $250 penalty, irrigation season), denverwater.org; "Backflow Assembly Test & Maintenance Report" (report by email; failed tests within 24 hours at 303-628-5969), PDF; "New Water Service Connections" (service line evaluation before building permits for major renovations; tap and meter set by Denver Water after meter pit inspection), denverwater.org. All read November 3, 2026.
18. Colorado Department of Public Health and Environment, "Backflow prevention and cross-connection control" (Regulation 11; HB25-1077 lets certified cross-connection control technicians inspect, test and repair backflow devices). cdphe.colorado.gov, read November 3, 2026.
19. Xcel Energy, "Service Guide Colorado: Natural Gas and Electric Installation" (revised April 2022): natural gas inspection requirements, meter set after an approved inspection, only Xcel Energy operates the inlet valve, Builders Call Line 800-628-2121. PDF, read November 3, 2026.
20. Colorado Division of Fire Prevention and Control, "Fire Suppression System Contractors" (Commercial, Civil & Residential; Residential Only; Backflow registrations), dfpc.colorado.gov; Denver Fire Department, "Fire Safety Systems Licensing" (installers of life safety systems, including sprinkler systems, need Denver Fire Department licenses), denvergov.org. Both read November 3, 2026.
21. City of Aurora, "Contractor Licensing and Lookup" (electricians and plumbers: state master's and contractor's licenses on file; no separate city license). auroragov.org, read November 3, 2026.
22. Pikes Peak Regional Building Department, "License Types" (P-A, RBC205.2.4) and "Licensing FAQ" (state licensees register immediately; RBC201.7 insurance certificate before registration; plumbing contractors $1,000,000/$2,000,000; lapse suspends). LicenseTypes, LicensingFAQ, read November 3, 2026.
23. City of Boulder, "Contractor Licensing" (Plumbing Contractor License; one master of record per licensee; no reciprocal licenses; $1,000,000 per occurrence and $2,000,000 aggregate general liability, City of Boulder additional insured; plumbing contractors may install fuel gas piping). bouldercolorado.gov, read November 3, 2026.
24. City of Fort Collins, "Contractor Licensing" FAQ (all contractors licensed; business license; master plumber registration without a city exam; masters listed on permits). fcgov.com, read November 3, 2026.
25. Colorado Department of Labor and Employment, Division of Workers' Compensation, "Workers' Compensation Insurance Requirements" (one or more employees; contractors without employees: a policy or a rejection of coverage). cdle.colorado.gov, read November 3, 2026.
26. Colorado Consumer Protection Act, C.R.S. 6-1-105(1)(z) (failing to obtain required licenses or permits), 6-1-112(1)(a) and (c) (up to $20,000 per violation, $50,000 against an elderly person), 6-1-113(2) (actual damages or $500, treble damages for bad faith, attorney fees). olls.info, Colorado Revised Statutes 2026, read November 3, 2026.
27. Benham v. Heyde, 122 Colo. 233, 221 P.2d 1078 (Colo. 1950). courtlistener.com, read November 3, 2026.
28. Carter v. Thompkins, 133 Colo. 279, 294 P.2d 265 (Colo. 1956). courtlistener.com, read November 3, 2026.
29. Aspen Drilling Co. v. Hayes, 876 P.2d 86 (Colo. App. 1994). courtlistener.com, read November 3, 2026.
30. EPA, "Lead Renovation, Repair and Painting Program" (authorized states, Colorado not among them; "all firms, even sole proprietorships"), epa.gov; 40 CFR 745.83 (minor repair and maintenance, including plumbing: 6 sq ft per room inside, 20 sq ft outside), law.cornell.edu. Both read November 3, 2026.
31. C.R.S. 12-115-116(8) and (9) (plugging in an appliance is not installing; appliance vendors may sell, deliver and connect appliances when no new wiring of the structure is needed). olls.info, Colorado Revised Statutes 2026, read November 3, 2026.
32. U.S. Bureau of Labor Statistics, Occupational Employment and Wage Statistics, May 2025, plumbers, pipefitters and steamfitters (47-2152): Colorado median $30.40 an hour, $63,240 a year; Denver-Aurora-Centennial metro $30.72 an hour (series OEUS080000000000047215208, OEUS080000000000047215213, OEUM001974000000047215208, via the BLS public data API). bls.gov, read November 3, 2026.