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Plumbing Permit in Thornton, Colorado

Required for plumbing installations, alterations, and repairs in Thornton. Governed by the 2024 International Plumbing Code (IPC) with Thornton amendments, effective July 1, 2025. The City of Thornton's Building Inspection Division issues and inspects plumbing permits inside city limits; plumbing contractors must hold a current State of Colorado Plumbing Contractor license and Master Plumber license as a prerequisite to the City's Plumbing Class D Specialty contractor license.

Verified 2026-06-30 · Source

When you need this permit

  • Plumbing contractor must hold a current State of Colorado Plumbing Contractor license (issued by DORA's State Plumbing Board) AND a City of Thornton Plumbing contractor license (Class D Specialty, $75.00) Contractor
  • Water heater installation/replacement, re-piping, new fixtures, and graywater systems require a permit
  • Homeowners doing plumbing work on their own private residence are exempt from the City contractor-license requirement, but the permit itself is still required
  • Governed by the 2024 International Plumbing Code (IPC) with Thornton amendments, effective July 1, 2025
  • Plumbing Data Worksheet (2024 IPC water fixture unit calculation) required when adding fixtures to an existing water service
  • Applications submitted via the CityView Portal

Required documents

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Fee schedule

Plumbing Permit Fee — trade valuation $0 to $1,000City of Thornton 2026 Building Permit Fee Schedule — 'Other Permit Fees including Mechanical, Electrical, Plumbing' table
$30.00
Plumbing Permit Fee — trade valuation $1,001 and up
$30.00 for the first $1,000 plus $10.00 for each additional $1,000 or fraction thereof
Mechanical, Electrical & Plumbing Fee — New Single Family Dwelling (combined)Flat fee when plumbing is part of a new single-family building permit rather than a standalone trade permit
$100.00
Lawn Sprinkler / Backflow (new residential or commercial)
$15.00
Sanitary Sewer — 1 unit
$11.00
Sanitary Sewer — 2 or more units
$8.00/unit
Contractor License — Class D Specialty (Plumbing)City of Thornton Contractor License Table: 'Plumbing (state and master licenses required)' — $75.00 Class D Specialty fee
$75.00

Review timeline

Plan reviewTypical estimate — confirm current times with the Thornton building department
~0–13 business days

How long did your Plumbing Permit permit actually take in Thornton?

Anonymous — one question, no email. Answers are combined and only shown once at least 5 people have reported.

Inspection process

  1. 1

    Underground / Under-slab

    Before concrete pour — verify pipe slope, materials, cleanouts

  2. 2

    Rough-In

    After pipes installed, before walls closed

  3. 3

    Final

    All fixtures connected, no leaks, proper venting verified

See the full Thornton inspection guide — scheduling & re-inspection fees →

Tips

  • The City of Thornton's Building Inspection Division — not a Colorado DORA state inspector — issues and inspects plumbing permits within Thornton city limits. A current State of Colorado Plumbing Contractor license and Master Plumber license are prerequisites to the City's own $75.00 Plumbing Class D Specialty contractor license. Contractor
  • Unlike the Electrical Class D Specialty license (no City fee), the Plumbing Class D Specialty license carries a $75.00 City fee.
  • Homeowners performing plumbing work on their own private residence are exempt from the City contractor-licensing requirement, but must still obtain the permit itself.

Frequently asked questions

Thornton requires a plumbing permit for: Plumbing contractor must hold a current State of Colorado Plumbing Contractor license (issued by DORA's State Plumbing Board) AND a City of Thornton Plumbing contractor license (Class D Specialty, $75.00); Water heater installation/replacement, re-piping, new fixtures, and graywater systems require a permit; Homeowners doing plumbing work on their own private residence are exempt from the City contractor-license requirement, but the permit itself is still required; Governed by the 2024 International Plumbing Code (IPC) with Thornton amendments, effective July 1, 2025; Plumbing Data Worksheet (2024 IPC water fixture unit calculation) required when adding fixtures to an existing water service; Applications submitted via the CityView Portal. If your project isn't listed, confirm with City of Thornton — City Development, Building Inspection Division at 303-538-7250 before starting work.

In Thornton, the published Plumbing Permit Fee — trade valuation $0 to $1,000 is: $30.00. Additional published fees: Plumbing Permit Fee — trade valuation $1,001 and up — $30.00 for the first $1,000 plus $10.00 for each additional $1,000 or fraction thereof; Mechanical, Electrical & Plumbing Fee — New Single Family Dwelling (combined) — $100.00; Lawn Sprinkler / Backflow (new residential or commercial) — $15.00; Sanitary Sewer — 1 unit — $11.00; Sanitary Sewer — 2 or more units — $8.00/unit; Contractor License — Class D Specialty (Plumbing) — $75.00. These are the jurisdiction's own published figures — see the fee schedule table and source citations on this page.

Plan review for a plumbing permit in Thornton typically runs 0–13 business days. This is an estimate, not a published figure — confirm current review times with City of Thornton — City Development, Building Inspection Division at 303-538-7250.

You'll need: Plumbing Permit Application (CityView Portal). Depending on your project, Thornton may also ask for: Plumbing Data Worksheet. See the required-documents checklist on this page for details on each.

Thornton requires 3 inspection(s) for a plumbing permit, in order: Underground / Under-slab, Rough-In, Final. Schedule each through City of Thornton — City Development, Building Inspection Division (303-538-7250).

Apply through City of Thornton — City Development, Building Inspection Division at 9500 Civic Center Drive, Thornton, CO 80229. Phone: 303-538-7250, email: buildings@thorntonco.gov. Office hours: Mon–Fri, 8:00 a.m.–5:00 p.m. (counter payments 8:00 a.m.–4:30 p.m.). Official information: https://www.thorntonco.gov/business-development/city-development/building-permits-inspections.

The City of Thornton's Building Inspection Division (buildings@thorntonco.gov, 303-538-7250) issues and inspects plumbing permits for all work within Thornton city limits. Plumbing contractors must separately hold a current State of Colorado Plumbing Contractor license and Master Plumber license (issued by DORA's State Plumbing Board) as a prerequisite to obtaining the City's Plumbing Class D Specialty contractor license ($75.00).

The 2024 International Plumbing Code (IPC) with Thornton amendments, effective July 1, 2025 — replacing the prior 2021 IPC cycle.

Sources & verification

Verified against official sources. Last reviewed 2026-06-30.

Fees, timelines, and adopted codes are researched from each jurisdiction's published records — see how we verify. Requirements change and vary by project, so always confirm the current details with the Thornton building department before you submit. PermitBase is an independent reference and is not affiliated with any government agency.

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