How Much Does It Cost to Install a Small Septic System?

Alison Kasch
Written by Alison Kasch
Updated October 4, 2021
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Installing a small septic system can cost between $2,910 and $18,600

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Whether you’re setting up a garage apartment or even a cottage off the grid, a septic system certainly beats an outhouse. Luckily, smaller systems are available, so you don’t have to pay for more than you need. Depending on your tank size, soil composition, and the type of system you want, costs can vary considerably.

How Much Does a Small Septic Tank System Cost by the Gallon?

If you’re looking to install a septic system, the smallest tank size you’re likely to find is 750-gallon, which will accommodate one to two bedrooms

You can also opt for a 1,000-gallon system, which will handle two to four bedrooms. Keep in mind that some municipalities require a minimum tank size of 1,000 gallons, so be sure to research the laws in your area. 

Here are some average costs for septic systems by tank size:

  • 750 gallons: $2,910–$13,900

  • 1,000 gallons: $4,030–$18,600

How Much Does It Cost to Install a Small Septic System Yourself?

As much as you might love rolling up your sleeves and getting your hands dirty, this is a job best left to the pros. Like most plumbing-related projects, there’s a lot that could go wrong, especially where human waste is concerned. Things could get really messy. Enough said.

What’s more, many places will require a licensed professional to install a septic tank system. There’s also the matter of meeting building code requirements, as well as passing inspections. In some cases, there may even be a fine for an illegally installed septic system. Save yourself the headache (and potential disaster): Hire a local septic tank installer instead.

Small Septic System Cost Breakdown

Conventional septic systems will require a tank, piping, and a leach (or drain) field. You’ll also need to factor in excavation, soil testing, and building permits. Below is a breakdown of what you might pay.

Small Septic Tank

The tank itself will run you between $750 and $1,500 based on its size and type. As mentioned earlier, some places require a minimum of 1,000 gallons, so be sure to check local laws. Here are some general ranges by size:

  • 750 gallons: $750–$1,200

  • 1,000 gallons: $900–$1,500

Leach Field

After wastewater gets separated and treated in the septic tank, it runs to a leach field. Here, it drains through soil, sand, and gravel, getting cleansed naturally before reaching the water table.

Depending on the type and size of your septic system, as well as your soil composition, leach field costs will vary significantly. Here are some rough estimates by size:

  • 750 gallons: $810–$19,000

  • 1,000 gallons: $1,080–$12,000

Excavation

Again, your tank size and soil composition will affect your excavation costs. Here’s what you might pay based on the size of your small septic tank:

  • 750 gallons: $200–$400

  • 1,000 gallons: $900–$1,800

Perc Test

A perc test will typically cost between $750 and $1,300. This test will determine the ground’s capabilities when it comes to absorbing and filtering water. For new installs, as well as repairs, you’ll need to show proof of this assessment.

Building Permits

Most places will require a building permit fee, ranging from $400 to $2,000. Costs will vary based on regulations in your area.

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How Much Does a Small Septic System Cost by Type?

There are three main types of septic tanks: concrete, plastic or poly, and fiberglass. Concrete is a common choice that can last a couple of decades, though it is vulnerable to cracking and separation. Plastic and fiberglass are more durable, but they are also more susceptible to damage during installation. Below are some general cost ranges to consider for each.

750-Gallon Septic Tank System

  • Concrete: $2,860–$13,900

  • Plastic/Poly: $2,660–$13,900

  • Fiberglass: $3,360–$13,900

1,000-Gallon Septic Tank System

  • Concrete: $3,830–$18,600

  • Plastic/Poly: $3,630–$18,600

  • Fiberglass: $4,330–$18,300

How Much Does a Small Septic System Cost by Style?

Traditional septic systems feature either an anaerobic or aerobic setup. Anaerobic systems are the most common, though aerobic septic systems are much more efficient (and costly).

Anaerobic Septic System

A small anaerobic septic system can run you between $3,000 to $8,000. This system relies on anaerobic bacteria, which are bacteria that don’t use oxygen. These bacteria work to break down waste within the septic tank before it gets further processed in the soil.

Aerobic Septic System

An aerobic septic system can cost anywhere from $10,000 to $18,600. These systems use oxygen-loving aerobic bacteria to break down waste more effectively. While this system calls for a higher budget, it breaks down waste in the tank more efficiently, saving you in leach field expenses.

What Factors Influence the Cost of a Septic Tank System?

Your septic system’s leach field has the biggest impact on overall cost, as prices vary considerably based on the size needed and the type of soil you have. Here’s a list of all the factors that might impact your small septic system cost:

  • Soil composition

  • The size and type of septic tank

  • The size of the leach field

  • Excavation and other labor costs in your area

  • Obtaining necessary building permits

FAQs About Septic Systems

How much does it cost to pump a septic tank?

Getting your small septic tank pumped costs anywhere between $290 and $530. Prices vary based on tank size and general usage. Get in touch with a local septic tank cleaner for an exact estimate. 

How do you know when to pump your septic tank?

Needing to pump the tank as soon as it “looks” full is a common myth about septic systems, as wastewater will eventually drain into the leach field. Instead, it’s better to determine how many solids have accumulated. A septic maintenance technician near you can test this to find out whether pumping is necessary.  

How much does it cost to repair a septic tank?

Repairing a septic tank costs between $500 and $2,600 on average, but prices will vary based on the repairs needed. Contact a local septic tank repair technician for an accurate cost estimate.

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