The quick “Do I need a licensed plumber?” rule
In Colorado, unlicensed plumbing work is illegal if the person is holding themselves out as a plumber / doing work that requires a license/permit/registration.
Under C.R.S. § 12-155-122, anyone who works as (or offers to work as) a plumber without an active license/permit/registration is subject to penalties. (Colorado Revised Statutes Section 12-155-122 (2024) - [Effective Until 7/1/2025] Unauthorized practice - penalties :: 2024 Colorado Revised Statutes :: U.S. Codes and Statutes :: U.S. Law :: Justia)
Homeowners can do plumbing work on their own home/property
Colorado explicitly says you don’t need a license to do plumbing work on your own property or residence. (Colorado Revised Statutes Section 12-155-118 (2024) - Exemptions :: 2024 Colorado Revised Statutes :: U.S. Codes and Statutes :: U.S. Law :: Justia)
But there’s a big “don’t get cute” exception:
If it’s rental property (occupied or to be occupied) or commercial/industrial, the owner is responsible and the property is subject to the licensing provisions (unless another exemption applies). (Colorado Revised Statutes Section 12-155-118 (2024) - Exemptions :: 2024 Colorado Revised Statutes :: U.S. Codes and Statutes :: U.S. Law :: Justia)
Verify Before You Pay
A real plumbing contractor in CO should be easy to verify:
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Use DORA’s official license lookup: Colorado Division of Professions and Occupations Online Services
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Ask for the contractor’s registration ID and the responsible master plumber’s registration ID.
And starting July 1, 2025: Colorado requires plumbing contractors to display both numbers on their vehicle(s), billing materials, bid sheets, and website. (Colorado Revised Statutes Section 12-155-125 (2024) - Plumbing contractors - requirement to display registration identification - master plumber of contractor :: 2024 Colorado Revised Statutes :: U.S. Codes and Statutes :: U.S. Law :: Justia)
If they can’t prove it on DORA + won’t show their numbers… that’s not a plumber. That’s a liability!
What a homeowner CAN do (without a plumbing license)
A) DIY allowed on your own home/property
Colorado allows homeowners to do plumbing work on their own property/residence. (Colorado Revised Statutes Section 12-155-118 (2024) - Exemptions :: 2024 Colorado Revised Statutes :: U.S. Codes and Statutes :: U.S. Law :: Justia)
B) Routine fixture swaps are specifically called out as allowed (license-wise)
The statute also says nothing prevents a person from employing someone to do routine repair/maintenance/replacement of:
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sinks, faucets, drains
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showers, tubs, toilets
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domestic appliances/equipment equipped with backflow preventers
So long as they are not installing new, moving or replacing the piping in the walls.
What you should absolutely hire a licensed plumber for (common scam zones)
This is your “Handyman Danger Zone” list — the stuff that causes floods, sewer gas, carbon monoxide risk, insurance denials, and/or failed inspections.
High-risk / high-consequence plumbing work (strongly recommended: licensed plumber)
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Water heater replacement (especially gas): gas, venting, T&P discharge, combustion air, seismic strapping rules in some areas
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Gas piping / moving gas lines for ranges, dryers, furnaces, tankless installs
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Sewer line repairs/replacements, mainline cleanouts, excavations, tie-ins
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New plumbing rough-in (bath remodels, basement finishes, additions)
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Moving supply/drain lines inside walls/slabs (kitchens, laundry, bathrooms)
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Backflow-related installs/removals (Colorado is picky here) (Colorado Revised Statutes Section 12-155-118 (2024) - Exemptions :: 2024 Colorado Revised Statutes :: U.S. Codes and Statutes :: U.S. Law :: Justia)
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Any “we’re just going to wing it” work that changes drainage, venting, or pipe sizing
If it can flood your house, gas your family, or contaminate the water… don’t hire just any guy-with-a-truck.
Permit & Inspections
Reality: permit requirements are often LOCAL, and inspection authority varies
Colorado’s plumbing program spells out that the state does not inspect in jurisdictions that have their own inspection program — meaning homeowners need to confirm whether state or local inspection authority applies at the address. (https://dpo.colorado.gov/EandP/Permits)
Contractor permits vs homeowner permits
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Colorado’s plumbing board says a Plumbing Contractor is required to obtain permits for company work, and work must not be done using a “homeowner” permit or a permit issued to another company. (Division of Professions and Occupations: Electrical and Plumbing Permits | Divisions of Professions and Occupations)
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Many local building departments also warn that homeowner permits are only for work the homeowner actually performs (example from PPRBD: homeowner permits only for primary residence, not rentals, and it’s illegal to pull a homeowner permit for a contractor). (Homeowner Permits - Pikes Peak Regional Building Department)
Colorado law even defines who can be a “qualified applicant” in the inspection/permit context, and it includes “a homeowner performing work on the homeowner’s home.” (Colorado Revised Statutes Section 12-155-120 (2024) - Inspection - plumbing permits - application - standards - definition :: 2024 Colorado Revised Statutes :: U.S. Codes and Statutes :: U.S. Law :: Justia)
Typically Requires a Permit/Inspections Checklist
Confirm with your city/county building department.”
Usually requires permit + inspection:
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Water heater replacement (especially gas)
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New plumbing in walls/floors (remodel rough-ins)
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Adding/moving drains/vents (DWV changes)
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New gas lines or gas appliance hookups
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Sewer line replacement/repair and new cleanouts (often)
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Adding new fixtures where plumbing is being extended (new bath, wet bar, laundry relocation)
May or may not require a permit depending on jurisdiction:
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Like-for-like fixture replacement (toilet, faucet, disposal, dishwasher)
Even if the state doesn’t require a plumbing license for some of these routine swaps, your local permit rules can still apply. (Colorado Revised Statutes Section 12-155-118 (2024) - Exemptions :: 2024 Colorado Revised Statutes :: U.S. Codes and Statutes :: U.S. Law :: Justia)
Red Flags
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“I don’t need a license, I’m a handyman.” (Cool. Then don’t touch the plumbing beyond basic fixture swaps.)
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No DORA listing / won’t provide license or registration numbers
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Wants homeowner to pull the permit “to save money”
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Cash-only + no contract + no warranty (the holy trinity of “good luck after I'm gone”)
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