Official sources checked August 30, 2026

Larimer County, Colorado septic permits and requirements

Colorado state and local framework

Colorado Regulation 43 establishes statewide minimum standards for onsite wastewater treatment systems. Colorado law also requires local boards of health to adopt detailed OWTS rules for their jurisdictions consistent with state requirements, so the county or local public-health agency is the key permitting authority for ordinary residential systems and may impose locally adopted procedures or requirements.

Larimer County Health requires a permit before building or repairing an OWTS

Larimer County states that state and county law require a permit from the Department before building or fixing a septic system. The county publishes its own OWTS application, instructions, fees, regulations, inspection guidance, and record-request process.

The permit category depends on the scope of work

Larimer distinguishes new-system, major-repair, minor-repair, sealed-vault, remodel-or-upgrade, and site-evaluation applications. A major repair includes replacement, expansion, or alteration of the soil treatment area, while tank replacement is treated as a minor repair.

Bedroom additions can trigger an OWTS upgrade review

Larimer states that a remodel or upgrade permit is used when the soil treatment area must be upgraded for a home addition or basement finish that adds bedrooms. Owners should therefore resolve OWTS capacity before assuming a residential building permit can proceed independently.

Sewer proximity affects new-system eligibility

Larimer’s current permit guidance states that a new OWTS is used for new construction or an additional building when a sewer connection is not available within 400 feet. Applicants should confirm sewer availability as part of the early feasibility review.

Limited-use systems are restricted

Larimer allows sealed vaults, vaulted privies, composting toilets, and similar limited-use systems only in qualifying circumstances. The county explains that seasonal or part-time use by itself is not enough to justify a limited-use system when a full OWTS can serve the property.

Graywater may not simply be discharged to the ground

Larimer County states that graywater from showers, laundry, and sinks must be treated and disposed of as wastewater under its OWTS regulations; direct discharge from a home or RV to the ground is prohibited.

County permit records can be checked before design or purchase decisions

Larimer provides online septic documents through its property-record system when available and a formal OWTS permit-record request process. It notes that many homes built before 1973 may not have permit records unless the system was repaired or upgraded later.

Official sources

• Colorado Secretary of State — Regulation 43, On-site Wastewater Treatment System Regulation
• Colorado Revised Statutes Title 25 — local boards of health and OWTS rules
• Larimer County — Septic Systems (OWTS)

SepticScope summarizes public-agency information for planning purposes. The permitting agency's current instructions control if they differ from this guide.