Plan to spend between $7,000 and $15,000 for a new septic system if you live on a relatively flat piece of land, according a 2014 report by the Boulder County Department of Public Health. If you plan to install a septic system on a sloped property or in the mountains, the price can soar as high as $35,000. Soil with poor drainage, high groundwater levels, and the presence of trees, boulders and other objects can also bump up costs.
All septic systems require a basic holding tank, which is sized based on the size of your household -- often going by the number of bedrooms and bathrooms in the house. An average residence typically requires a 1,000-gallon tank, though this figure can vary based on the property or on local requirements. Expect to pay around $1,000 for a 1,000-gallon basic tank, or over $2,000 for a 1,000-gallon heavy-duty tank, according to an April 2013 report by American Concrete Industries of Bangor, Maine. Larger tanks cost even more -- up to $3,895 for a heavy-duty 2,000-gallon unit.
Unless you plan to dig up the dirt yourself, don't forget to include installation costs in your septic system budget. The Catskill Watershed Corporation estimates the cost of excavating, installing a new septic tank, backfilling and replacing the landscaping at $2,494 to $2,989 as of April 2014. This price also includes removing and decommissioning an old septic tank, if one is present.
Leach fields come in two main varieties. The most common, and most economical, consists of gravel and perforated piping. Prices vary from $10.82 per linear foot for 4-inch piping to $10.32 per linear foot for 2-inch piping, according to an April 2014 report by Catskill Watershed Group. This price includes leach field excavation, backfill, pipe, gravel bedding and fittings. In most cases, using infiltration chambers costs more than the pipe-and-gravel system, except in areas where local gravel costs are relatively high. In these areas, the costs of hauling in gravel can make plastic or concrete infiltration chambers the more economical choice.
When you plan your budget, don't forget to add in extras that may pop up. Prepare to pay between $700 and $1,500 for an engineer to evaluate the soil and design your system, according to the Boulder County Department of Public Health. Factor in the cost of permits, which vary by city, but can easily cost several hundred dollars. Finally, prepare to spend $250 to $300 every few years to maintain your system, estimates the U.S. Environmental Protection Agency.