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)
- 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
- Req
Plumbing Permit Application (CityView Portal)
Online application through the City of Thornton's CityView Portal
- Opt
Plumbing Data Worksheet
2024 IPC water fixture unit (F.U.) calculation, required for fixture additions to an existing water service
Fee schedule
| Fee type | Amount | Notes |
|---|---|---|
| Plumbing Permit Fee — trade valuation $0 to $1,000 | $30.00 | City of Thornton 2026 Building Permit Fee Schedule — 'Other Permit Fees including Mechanical, Electrical, Plumbing' table |
| 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 | Flat fee when plumbing is part of a new single-family building permit rather than a standalone trade permit |
| 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 | City of Thornton Contractor License Table: 'Plumbing (state and master licenses required)' — $75.00 Class D Specialty fee |
Review timeline
~0–13 business days
Typical estimate — confirm current times with the Thornton building department
Inspection process
- 1
Underground / Under-slab
Before concrete pour — verify pipe slope, materials, cleanouts
- 2
Rough-In
After pipes installed, before walls closed
- 3
Final
All fixtures connected, no leaks, proper venting verified
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.
- 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
- Who issues plumbing permits in Thornton — the city or the State of Colorado?
- 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).
- What plumbing code does Thornton use?
- 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.
- City of Thornton — City Development, Building Inspection Division — official building department
- City of Thornton 2026 Building Permit Fee Schedule (PDF)
- Ordinance Adopting 2024 I-Codes — Sec. 10-153, International Plumbing Code adopted by reference
- City of Thornton Contractor License Information and Forms (PDF, includes Contractor License Table)
- Colorado DORA — Division of Professions and Occupations, Plumbing Board: Permit and Inspection Information
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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