Septic permit rules and requirements in Montana
In Montana, the state sets the rule. The septic permit comes from your local health department. For some systems the state issues it itself. The code is Circular DEQ 4. Montana Department of Environmental Quality — Circular DEQ 4 (December 2023 Edition) · checked 2026-09-12
Engineering Infrastructure & Subdivisions
Writes the rules
checked 2026-09-23
Your local health department
Issues the permit
checked 2026-09-12
Circular DEQ 4
Code section
checked 2026-09-23
Who decides a septic permit in Montana
Your local health department issues an ordinary residential permit. For some systems the state issues it itself. The state sets the floor through the Engineering Infrastructure & Subdivisions, Montana Department of Environmental Quality.
The circular names the department as a reviewing authority. A local health board can also become one. State law lets it too. So both the state and local boards can approve plans for the same system.
Montana Department of Environmental Quality — Circular DEQ 4 (December 2023 Edition) · checked 2026-09-12
The office's phone number is 406-444-5546.
This is the phone number for the on-call engineer. Staff there answer questions on subdivision and septic design. The page lists other numbers too.
Montana Department of Environmental Quality — Engineering Infrastructure & Subdivisions, Program Contacts · checked 2026-09-23
The office publishes its own page on this: Montana Department of Environmental Quality — Engineering Infrastructure & Subdivisions.
This is the program's own page on the department's site. The page carries no separate canonical link.
Montana Department of Environmental Quality — Engineering Infrastructure & Subdivisions · checked 2026-09-23
The floor state law sets
The rules that govern every septic system in Montana are Circular DEQ 4 — Montana Standards for Subsurface Wastewater Treatment Systems. Every local permit is issued under them.
The circular sets minimum rules for the design of septic tanks and drainfields. A local health board can adopt these rules.
Montana Department of Environmental Quality — Circular DEQ 4 (December 2023 Edition) · checked 2026-09-23
Montana counties on this site
We have not published a Montana county page yet. A county earns a page when we hold facts unique to it. Until then this page is the answer for every county in the state.
Telling us your county is how we decide which one to build next.
Sources
State records only. Each figure above has a government source and a checked-on date. County figures live on the county pages.
Verify before you act. Septic rules are set locally and they change. Check anything here with your local health department before you spend money on it.