Montana plumbing rules
Whether a plumber has to be licensed in Montana, how to check one, when you need a permit and who issues it, which code the state adopted, and how deep a water line has to be buried in Missoula, Billings and Great Falls. Every figure links the statute, rule or city standard it came from.
- Last updated 2026-08-31
- Primary sources only
- 14 answers
By city
Water service depth is not the same number as footing depth
| City | Water service depth | Footing depth | Water hardness | Median year built | Jan average low |
|---|---|---|---|---|---|
| Missoula City of Missoula, inside city limits. Missoula County is separately certified for the rest of the county. Permit office | 6.0 ft | 36 inMissoula County figure; the city does not publish its own. | 163 mg/L average (9.45 grains per gallon) | 1981 | 18 °F |
| Billings City of Billings, inside city limits only. Outside the city the state Building Codes Bureau has jurisdiction, because Yellowstone County is not certified. Permit office | 6.5 ft | 42 in | 53.5 to 197 ppm range, no average published | 1980 | 17.9 °F |
| Great Falls City of Great Falls, inside city limits. A general plumbing permit is required whenever water service piping is repaired, altered or installed. Permit office | 6.5 ft | 42 in | 145 mg/L in finished water | 1965 | 15 °F |
Licensing
Does a plumber have to be licensed in Montana?
Yes. Montana law requires anyone working in the field of plumbing to hold a journeyman or master plumber licence issued by the Montana Board of Plumbers, and to carry the licence or proof of it on the job site. The exemptions are listed separately in MCA 37-69-102.
- Montana Code Annotated 37-69-301 (MCA 2025)
- Montana Board of Plumbers, Department of Labor and Industry (accessed 2026-08-31)
How do I check whether a Montana plumber is licensed?
The Montana Department of Labor and Industry runs a public licensee lookup. Search the plumber's name or business there and it returns the licence type and status. A licensed plumber is also required to carry the licence or proof of it on the job, so you can ask to see it.
- Montana DLI public licensee lookup (accessed 2026-08-31)
What plumbing licence classes exist in Montana?
Montana issues a Journeyman Plumber licence and a Master Plumber licence, plus a Medical Gas endorsement. A journeyman may only work in the employment of a licensed master plumber unless board rule permits otherwise. Every plumbing business also designates one Master Plumber of Record who supervises its plumbing work.
Can I do my own plumbing in Montana without a licence?
The owner of a single-family residence used exclusively for their own personal use may install sanitary plumbing and potable water supply piping in it without a plumbing licence. That exemption is one of several in MCA 37-69-102, which also covers farms and ranches not on public water or sewer, and registered apprentices under supervision.
- Montana Code Annotated 37-69-102 (MCA 2025)
Is there a Montana plumbing contractor licence?
No. Montana issues journeyman and master plumber licences, not a plumbing contractor licence. Montana does have a separate construction contractor licence, and a plumber licensed in Montana operating within the scope of that licence is expressly exempt from it. Advertisements for a Montana plumbing contractor licence are describing something that does not exist.
- Montana Code Annotated 37-45-104(16) (MCA 2025)
Did Montana contractor registration change?
Yes. Montana's construction contractor registration became a contractor licence on 1 January 2026 under House Bill 239 of the 2025 session, administered by the Department of Labor and Industry. Existing registrations converted automatically. The law moved to MCA Title 37, Chapter 45; the old Title 39, Chapter 9 has been renumbered and repealed.
Permits
Do I need a plumbing permit in Montana?
Montana law makes it unlawful to install, remove, alter or repair plumbing and drainage systems without first obtaining a permit, with a separate permit for each building. Minor replacement or repair with no significant potential to create a hazard is exempt, as is a residential property owner personally doing their own sanitary plumbing and potable water supply piping.
- Montana Code Annotated 50-60-505 (MCA 2025)
- Montana Code Annotated 50-60-506 (MCA 2025)
Who issues the plumbing permit, the state or the city?
Whichever has jurisdiction. A state permit is not required where a county, city or town has its own building code covering plumbing with inspection procedures. Everywhere else falls to the state Building Codes Bureau. Missoula, Billings and Great Falls are all certified for plumbing and issue their own permits inside city limits.
- Montana Code Annotated 50-60-506(3) (MCA 2025)
- Montana Building Codes Bureau, certified local governments (list updated 2025-08-14)
Which plumbing code has Montana adopted?
Montana has adopted the Uniform Plumbing Code, 2021 edition, not the International Plumbing Code. The adoption is in Administrative Rules of Montana 24.301.301, effective 11 June 2022, and it also adopts UPC appendices A, B, C, D, K, L, M and N.
- Administrative Rules of Montana 24.301.301 (effective 2022-06-11)
- Montana DLI current codes (accessed 2026-08-31)
Burial depth and frost
How deep does a water service line have to be buried in Montana?
It is set by the city, not by one statewide number. Missoula requires a minimum 6.0 feet of cover on water services. Billings requires 6.5 feet. Great Falls requires 6.5 feet below final street grade and finished grade, and less depth needs staff approval plus insulation.
- City of Missoula Standards and Specifications Manual, section 02660 (January 2026, Rev. 1)
- City of Billings standard modifications to MPWSS, 6th edition, 3.8.A (January 2021)
- City of Great Falls Standards for Design and Construction, 5.2.1.C (Rev. 4, 2025-06-09)
Is the Montana frost depth 42 inches?
42 inches is a footing depth, and it is not the water line depth. Billings and Great Falls both publish 42 inches to the bottom of footings; Missoula County publishes 36 inches. Water service lines in those same cities have to be 6 to 6.5 feet deep. The two numbers are frequently confused.
- City of Billings design criteria (accessed 2026-08-31)
- City of Great Falls construction guide (accessed 2026-08-31)
- Missoula County climatic and geographic design criteria, IRC Table R301.2 (February 2024)
How cold does it actually get in these towns?
On the NOAA 1991 to 2020 climate normals, the average daily minimum in January is 18.0 degrees Fahrenheit at Missoula International, 17.9 at Billings Logan International, and 15.0 at Great Falls International. Great Falls is the coldest of the three by that measure, and January is its coldest month.
- NOAA NCEI US monthly climate normals, 1991 to 2020 (released 2021)
Water hardness and housing stock
How hard is the water in Missoula, Billings and Great Falls?
Missoula reports an average total hardness of 163 mg/L as calcium carbonate, which the city also prints as 9.45 grains per gallon. Great Falls reports 145 mg/L in finished water. Billings publishes a range of 53.5 to 197 ppm and no annual average. All three are moderately hard to hard, which is what shortens water heater life.
How old is the housing stock in these towns?
By the Census Bureau's 2024 five-year American Community Survey, the median year a structure was built is 1981 in Missoula, 1980 in Billings, and 1965 in Great Falls. Great Falls housing is roughly fifteen years older at the median, which matters for galvanised supply lines and cast iron drains.
- US Census Bureau, ACS 5-year table B25035, median year structure built (2024 ACS 5-year, 2020 to 2024)
What is not on this page, and why
- A City of Missoula frost depth. The county publishes 36 inches; the city publishes none.
- Grains per gallon for Billings and Great Falls. Neither city publishes it, and converting from mg/L would make the figure ours rather than theirs.
- An annual average hardness for Billings. The city publishes a range only.
- The share of Montana homes on crawl spaces. The American Housing Survey samples 35 large metros and none are in Montana.
These are published nowhere we could find at a primary source. Rather than convert a unit or take a midpoint and present it as cited, they are left out and listed here.
One call instead of nine.
The usual way to find a plumber is to phone down a list and leave voicemails.
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- Free to you. No fee, no signup, no account
Covering Missoula, Billings, Great Falls and the surrounding communities.