If you’re planning a new septic system installation or replacement in Northern Colorado, the cost estimate you may get from your septic contractor can vary by tens of thousands of dollars depending on the system and the property.
A basic gravity-fed system can cost around $20,000–$35,000, while advanced or engineered systems can reach $30,000–$45,000+. Drain field and tank replacements have their own price ranges, and your county, soil conditions, property layout, and required system design can all change the final estimate.
The costs below are estimates that include all engineering, permitting, and installation. They are for planning purposes only. For an actual septic system estimate tailored to your project in Northern Colorado, please send us a message or call 970-342-0214 today.
What You’re Installing: Cost Breakdown by Septic System Type
The type of septic system your property requires is one of the biggest factors affecting the total cost. A septic system typically includes a tank and a soil treatment area, or drain field. Depending on the site, the system may also require pumps, advanced treatment equipment, pressure distribution, or other components.
1. Traditional Gravity-Fed Systems (Full Installation/Replacement)
Estimated Cost: $20,000–$35,000
A traditional gravity-fed system is generally the simplest type of septic system, where wastewater moves from the home into the septic tank, then into the drain field without relying on a pump to distribute it throughout the field.
This estimated cost includes the site and soil evaluation, septic system design, permit fees, septic tank, drain field, excavation, labor, and basic site restoration.
Traditional systems can be on the lower end of this price range when the property has suitable soil, enough space, favorable slopes, and enough separation from groundwater or bedrock. The biggest factors that can push your septic system toward the higher end of this price range are a larger house size, tough soils, or ground water requiring a hybrid system, like this one we installed recently in Pierce, CO.
2. Advanced or Engineered Septic Systems (Full Installation/Replacement)
Estimated Cost: $30,000–$45,000+
Not every property can use a basic gravity-fed system, like when there are challenging soil conditions, shallow groundwater, limiting soil layers, steep slopes, limited space, or other constraints. These constraints will require a more complex design, or specially engineered septic system. This may include pressure distribution, pumps, control panels, mound systems, sand filters, or another engineered approach.
Advanced systems cost more because they require additional design, excavation, equipment, electrical work, and ongoing components that aren’t necessary with a basic gravity system.
3. Drain Field Installation/Replacement Only
Estimated Cost: $15,000–$40,000
If your septic tank is still serviceable but the drain field has failed, you may not need to replace the entire system. A drain field replacement would involve engineering a new soil treatment area, excavating it, and connecting it to the existing septic tank when the existing components can be reused.
For every drain field replacement, the available space, soil conditions, excavation requirements, engineering costs, and how accessible the property is will all factor into your estimate.
The wide range in cost here reflects the type of replacement field required. For a traditional gravity-fed drain field, your estimate will be more around $15,000–$30,000 (depending on size of the house, soils, groundwater, and placement of the field). For pressure dosed drain field replacements, which are rare, your estimate may be more in the $20,000–$40,000 range. The higher estimate factors in the potential replacement of a pump tank, adding/replacing your pump, and any electrical work required for this specialized system.
4. Septic Tank Installation/Replacement Only
Estimated Cost: $7,000–$25,000
Replacing only your septic tank can be significantly less expensive than replacing the whole system, provided that the drain field and other components are still usable.
Here, the price range fluctuates a lot based on tank size, tank material, tank location, accessibility for excavation equipment, existing plumbing, and groundwater conditions.
- A traditional gravity-fed septic tank typically ranges from $7,000–$10,000. The biggest factors here are tank depth and tank material (plastic or concrete).
- A pressure dosing septic tank replacement varies more. The holding tank is typically in the same $7,000–$10,000 range as a gravity-fed tank. Replacing the pump tank can cost $5,000–$15,000, depending on whether the pump, control panel, or other components also need replacing. For larger, three-compartment concrete tanks, where the holding tank and pump tank are cast together, the project can reach $20,000–$25,000 if the tank and major components all need to be replaced.
Pricing for these various replacements will also vary by County because of different permitting costs, which we break down below. For example, all septic tank replacements in Jefferson County require engineering, which will be reflected in your estimate.
Where You’re Installing: Cost Breakdown by County
Two properties with similar homes can even have very different septic costs just because they’re located in different counties. Northern Colorado’s septic systems are regulated locally, so permit fees, application requirements, inspections, and other general requirements will vary by county.
1. Septic System Cost in Weld County
Weld County’s 2026 On-Site Wastewater Treatment System (OWTS) permit fee is $1,500 for a standard OWTS permit, while an OWTS repair or alteration permit is $1,100.
For a new or replacement system, Weld County requires a site and soils evaluation and design documentation. An engineered design signed and stamped by a professional engineer may also be required depending on the project. The county conducts a site inspection before issuing the permit.
When budgeting for a Weld County septic project, account for:
- Site & Soil Evaluation: Cost varies by property and provider
- Engineering & Design: Cost varies by property and provider
- Permit: $1,500 for a standard permit
- Drain Field: ~$14,000–$25,000+ including labor
- Tank: ~$7,000–$11,500+ including labor
- Total: ~$21,000–$35,000+
Includes full installation package: design, permits, materials, labor, etc.
2. Septic System Cost in Larimer County
Larimer County’s 2026 fees include $1,881 for a new OWTS permit, $1,320 for a major repair or remodel permit, and $750 for a minor repair involving only a septic tank. The county also requires a $290 site evaluation fee.
For a new system, Larimer County requires a soil report and sketch plan. Certain site conditions will require professional engineering, including specific soil classifications, percolation rates outside the permitted range, or shallow bedrock/groundwater.
When budgeting for a Larimer County septic project, account for:
- Site & Soil Evaluation: Cost varies by property and provider
- Engineering & Design: Cost varies by property and provider
- Permit: $1,881 for a standard permit ($1,320 for a repair/remodel, $750 for a tank-only repair)
- Drain Field: ~$15,000–$29,000+ including labor
- Tank: ~$7,000–$11,500+ including labor
- Total: ~$21,000–$35,000+
Includes full installation package: design, permits, materials, labor, etc.
3. Septic System Cost in Boulder County
Boulder County’s septic regulations can be more stringent than the baseline state requirements, which can affect both design and project cost. Boulder County currently has a $3,023 fee for a new construction OWTS permit (2026), which includes several inspections and services associated with the permit.
When budgeting for a Boulder County septic project, account for:
- Site Evaluation: Cost varies by property and provider
- Engineering & Design: Cost varies by property and provider
- Permit: $3,023 for a new construction permit, $1,823 for a major repair, or $1,223 for a minor repair such as septic tank replacement
- Drain Field: ~$22,000–$29,000+ including labor
- Tank: ~$10,000–$11,500+ including labor
- Total: ~$35,000–$45,000+
Includes full installation package: design, permits, materials, labor, etc.
4. Septic System Cost in Jefferson County
Jefferson County has a lot of mountain and foothill properties, so site conditions can play more of a role here than other areas in Northern Colorado. Mountain access, rocky soil, smaller lots, and higher-level treatment will all be location-specific cost considerations.
When budgeting for a Jefferson County septic project, account for:
- Site Evaluation: Cost varies by property and provider
- Engineering & Design: Cost varies by property and provider
- Permit: $1,523 for a new system permit or $773 for a single-component permit, such as a septic tank or soil treatment area
- Drain Field: ~$15,000–$30,000+
- Tank: ~$10,000–$12,000+
- Total: ~$27,000–$44,000+
Includes full installation package: design, permits, materials, labor, etc.
Special Considerations that May Affect Your Project Cost
Tight Lots
A tight lot can make septic work more difficult, especially when you’re replacing an existing septic system and there is limited room for a new soil treatment area. If there is not enough open space to work with, the system may require a different layout or additional engineering to make everything fit within the required setbacks.
Tank Depth
Weld County and Larimer County limit the depth of an absorption field to 4 feet below the original grade. If the site requires a deeper tank or other components because of the property’s elevation or layout, additional excavation or equipment may be needed which will be reflected in your system cost.
Mountain Locations
Some septic projects in the mountain areas in Boulder County or Jefferson County along the Front Range can cost more because of the site itself. Hard rock can make excavation slower or more difficult, while steep or difficult-to-access properties may also require additional labor to get materials and machinery where they need to go.
Complex Soils
Northern Colorado has a huge range of soil types across the counties, like sandy or loamy soils in one area and heavy clay, gravel, rock, or restrictive layers in another. Those conditions affect how the soil can treat and move wastewater and can change how the system itself needs to be designed.
Get a Detailed Estimate on Your Septic System Replacement in Northern Colorado
Published cost ranges can help you budget, but they can’t tell you what your property will require. An on-site evaluation gives you a much clearer picture of the system, work, and cost involved before you commit to the project.
Call us at 970-342-0214 or send us a message today to get started.
Ace Septic & Excavation is a septic contractor specializing in septic repair and replacement in Northern Colorado, including Weld County, Larimer County, Boulder County, and Jefferson County.