In Colorado, onsite wastewater (septic) systems are regulated by Colorado Department of Public Health and Environment (CDPHE), Water Quality Control Division — implementing rules adopted by the Water Quality Control Commission, which sets the statewide code, and permits are issued and inspections carried out by county or local health jurisdictions. Installing, replacing or repairing a septic system here means, in sequence: a site and soil evaluation, a design, a permit application, an inspection while the system is open, and a final as-built record once it is approved.
The state-level regulator is Colorado Department of Public Health and Environment (CDPHE), Water Quality Control Division — implementing rules adopted by the Water Quality Control Commission (official program page). The Water Quality Control Commission sets minimum statewide standards via Regulation 43, but for systems with design flows of 2,000 gallons per day or less (nearly all residential septic) permitting is carried out by county/local public health agencies, each of which adopts its own regulation at least as stringent as Reg 43. Systems above 2,000 gpd instead go through the state Division's facility design review and approval process.
The statewide onsite-wastewater code is cited as Regulation No. 43 — On-Site Wastewater Treatment System Regulation, 5 CCR 1002-43 (promulgated under the On-site Wastewater Treatment System Act, C.R.S. 25-10-101 et seq.). We link the agency's own page above rather than restating specific numeric requirements from it, since those change by rule revision and by local amendment.
The order of operations is broadly consistent across the country, even though the specific numbers in each step vary by state and often by county. None of the figures below are specific to Colorado; treat this as the shape of the process, and get the actual numbers from the agency linked above or from the county office.
| Design | A "Designer, on-site wastewater treatment system" as defined in Reg 43 prepares the design; a Colorado-licensed Professional Engineer is specifically required for higher-risk conditions (poor/type-R soils, higher treatment levels, shallow groundwater or bedrock, steep slopes, pressure distribution, commercial/multi-family systems, wastewater ponds) per Reg 43 section 10.B. https://www.sos.state.co.us/CCR/GenerateRulePdf.do?ruleVersionId=7614&fileName=5+CCR+1002-43 |
|---|---|
| Installation | "Systems contractor" as defined in Reg 43 — installs, renovates, and repairs OWTS. Local boards of health may adopt licensing of systems contractors (and systems cleaners); the license is issued and administered by the local public health agency under Reg 43 section 5.K, not directly by the state. https://www.sos.state.co.us/CCR/GenerateRulePdf.do?ruleVersionId=7614&fileName=5+CCR+1002-43 |
Septic records in Colorado are generally held by the county or local health jurisdiction that issued the permit, not by the state agency, and are released under the state's public records law. We have not logged the specific statute name and response deadline for Colorado yet; check with the county office listed on its records page below, or with Colorado Department of Public Health and Environment (CDPHE), Water Quality Control Division — implementing rules adopted by the Water Quality Control Commission.
We hold 33,409 septic records across 35 of 64 Colorado counties. Each county page below shows exactly where its records are kept and how many we hold.
| County | Records held |
|---|---|
| Douglas | 14,690 |
| Arapahoe | 13,964 |
| Weld | 2,554 |
| Jefferson | 1,224 |
| Fremont | 328 |
| Garfield | 248 |
| Alamosa | 67 |
| Mesa | 62 |
| Washington | 34 |
| Gilpin | 29 |
| Conejos | 24 |
| Las Animas | 23 |
| Park | 20 |
| Saguache | 17 |
| Lake | 17 |
| San Miguel | 15 |
| Delta | 11 |
| Logan | 10 |
| Rio Grande | 10 |
| Hinsdale | 9 |
| Archuleta | 9 |
| Dolores | 8 |
| Ouray | 6 |
| El Paso | 6 |
| Montrose | 5 |
| Otero | 5 |
| Grand | 2 |
| Montezuma | 2 |
| Teller | 2 |
| Phillips | 2 |
| Elbert | 2 |
| Denver | 1 |
| Rio Blanco | 1 |
| Pitkin | 1 |
| Broomfield | 1 |
Full Colorado county-by-county index · Open the parcel map
Colorado Department of Public Health and Environment (CDPHE), Water Quality Control Division — implementing rules adopted by the Water Quality Control Commission. The Water Quality Control Commission sets minimum statewide standards via Regulation 43, but for systems with design flows of 2,000 gallons per day or less (nearly all residential septic) permitting is carried out by county/local public health agencies, each of which adopts its own regulation at least as stringent as Reg 43. Systems above 2,000 gpd instead go through the state Division's facility design review and approval process.
The sequence is a site and soil evaluation, a design sized from the evaluation and (under most state codes) bedroom count, a permit application, an inspection before backfill, and a final as-built filed once the system is approved. Exact numeric requirements are set by the agency's own code, not restated here.
"Systems contractor" as defined in Reg 43 — installs, renovates, and repairs OWTS. Local boards of health may adopt licensing of systems contractors (and systems cleaners); the license is issued and administered by the local public health agency under Reg 43 section 5.K, not directly by the state. https://www.sos.state.co.us/CCR/GenerateRulePdf.do?ruleVersionId=7614&fileName=5+CCR+1002-43
Septic records are generally held by the county or district health office that issued the permit. See our county-by-county Colorado index for the specific office and portal in each county.
Regulatory information on this page was researched against official state agency sources and last verified 2026-08-31. It is informational only: the agency linked above is authoritative, and requirements can change. We are not lawyers, not a government body, and not affiliated with, licensed or certified by any agency named on this page.