SepticSmart: Cost of Installation or Repair

SepticSmart: Cost of Installation or Repair

Approximate Cost of Installation or Repair

The cost of installing or repairing an onsite wastewater system (OWD, or septic system) is the most important factor to many people. Most types of OWS are of the conventional type, consisting of a septic tank and an absorption field.

The septic tank, which usually has a capacity of about 1,000 gallons and is composed of two compartments, is buried in the ground in series with a gravel-filled bed or a number of gravel-filled trenches. The property must be large enough to accommodate the septic tank and the absorption field.

Generally, at least 1 acre of land is needed for an OWS to function adequately. The following information is presented in order to give residents of Boulder County the necessary cost information when planning an OWS installation or repair.

Establishing Cost to Repair or Replace

There are many factors involved in the price of an OWS, including, but not limited to:

  • Location: The property location is the most important factor. Installation of an OWS in the plains on flat ground can range from $7,000 to $15,000, while installation in the mountains can range from $10,000 to $35,000.
  • Substrate: The ability of the soil surrounding the drain field to absorb and treat the effluent is an important concern in regard to water quality, as is the composition of soil on the property. Rocky soil will require extensive excavation work and will require imported soil for bedding, while a clay soil will require a larger absorption area and more construction materials.
  • Level of Water Table: An OWS installed in an area of high groundwater will require imported soil to raise the system to a height where effluent can be adequately treated in the soil prior to entering the groundwater. The imported soil will need to be re-percolated by the design engineer to verify its suitability to treat the effluent.
  • Property Terrain: Slope is an important factor, as leveling the leach field on a hill will require more extensive excavation. Removal of objects, such as trees and boulders, will also increase the cost of excavation.
    Property Size: Especially when replacing a system, property size can affect cost. When replacing the leach field, most installers will simply install a second field; however, if there is not sufficient room for a second field, the original field will need to be excavated and hauled away, resulting in a significantly higher cost.
  • House Size: The number of bedrooms in your home legally determines the size of the OWS that must be installed.

The above factors are major components of an OWS install or repair price. The following figures are from actual OWS repairs or replacements in Boulder County:

  • Minor Repair: Costs ranged from $2,100 to $3,920, with an average cost of $3,066.
  • Major Repair: Costs ranged from $4,860 to $21,800, with an average cost of $9,173.
  • New System: Costs ranged from $7,790 to $35,000, with an average cost of $14,866

Hiring an Engineer

The costs of hiring, an engineer can range from $700 to $1,500, but certain sites may be more difficult, and engineer costs can range up to $2,000.


Financial Assistance

A low-interest loan program is in place to help low to moderate-income households construct or repair onsite wastewater systems.

Please Note: This information is intended to provide a better understanding of the functions of onsite wastewater treatment and the need for proper design, installation, and maintenance. Always consult a licensed professional or public health official with questions regarding engineering, installation, and servicing of onsite wastewater systems.

Contact Us

SepticSmart Program

Main: 303-441-1564
Submit a question


3450 Broadway
Map & Directions
Hours: 8 a.m. - 4:30 p.m. M-F