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Colorado Plumbing: When to DIY vs Hire a Licensed Plumber
Learn when Colorado homeowners can DIY plumbing, when permits and inspections are required, and when hiring a licensed plumber protects your home and wallet.
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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)

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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)

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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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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)

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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

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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)

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B) Routine fixture swaps are specifically called out as allowed (license-wise)

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The statute also says nothing prevents a person from employing someone to do routine repair/maintenance/replacement of:

  • sinks, faucets, drains

  • showers, tubs, toilets

  • domestic appliances/equipment equipped with backflow preventers

(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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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.

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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

  • Gas piping / moving gas lines for ranges, dryers, furnaces, tankless installs

  • Sewer line repairs/replacements, mainline cleanouts, excavations, tie-ins

  • New plumbing rough-in (bath remodels, basement finishes, additions)

  • Moving supply/drain lines inside walls/slabs (kitchens, laundry, bathrooms)

  • 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)

  • Any “we’re just going to wing it” work that changes drainage, venting, or pipe sizing

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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)

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Contractor permits vs homeowner permits

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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)

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Typically Requires a Permit/Inspections Checklist

Confirm with your city/county building department.”

 

Usually requires permit + inspection:

  • Water heater replacement (especially gas)

  • New plumbing in walls/floors (remodel rough-ins)

  • Adding/moving drains/vents (DWV changes)

  • New gas lines or gas appliance hookups

  • Sewer line replacement/repair and new cleanouts (often)

  • Adding new fixtures where plumbing is being extended (new bath, wet bar, laundry relocation)

 

May or may not require a permit depending on jurisdiction:

  • 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

  • “I don’t need a license, I’m a handyman.” (Cool. Then don’t touch the plumbing beyond basic fixture swaps.)

  • No DORA listing / won’t provide license or registration numbers

  • Wants homeowner to pull the permit “to save money”

  • Cash-only + no contract + no warranty (the holy trinity of “good luck after I'm gone”)

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