How Much Does a Small Septic System Cost to Install? [2025 Data]
The cost to install a small septic system goes from $2,910 to $18,600, with an average of $4,100 on professional installation. Costs vary depending on tank size, type of system, and soil composition.
The tank capacity and the drain field size are the most important factors to consider and can swing your costs by thousands.
Choose your tank material and septic system type carefully. High-end tanks and complicated aerobic systems can cost much more than simple anaerobic systems with plastic tanks.
Have a professional size the system for your home, as tanks that are too big or too small will require additional pumping and maintenance that can add up.
Septic system installation or resizing requires a percolation test. The cost for this varies by area and can add significantly to your total.
A small septic system costs between $2,910 and $18,600, with an average of $4,100 for a smaller system.
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.
Small Septic System Cost by Tank Size
If you’re looking to install a small septic system, the smallest tank size you’re likely to find is 500 gallons. However, many municipalities have strict requirements for septic tank size, and they often require 750 gallons or even 1,000 gallons at minimum. Check with your local regulatory agency or get in contact with a septic pro to make sure your wastewater project abides by local laws.
| Tank Size in Gallons | Household Size | Average Cost With Installation |
|---|---|---|
| 500 | 1 bedroom | $875–$1,150 |
| 750 | 1 to 2 bedrooms | $2,910–$13,900 |
| 1,000 | 2 to 4 bedrooms | $4,030–$18,600 |
I had another company design my septic system replacement, but Paul re-designed it to avoid having to remove a 50+ ft tall tree and added a drainage system for the water from the gutters. The old no-longer-up-to-code 2-cesspool septic system was replaced by a drainfield and Ecoflow septic tank. The work was done on the days I was told workers would be here (unlike the company that drew up the first set of specs), and Paul and Jon were always friendly and great to work with.
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) and 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 $500 and $1,500 based on its size and type. As mentioned earlier, some places require a minimum of 750 or 1,000 gallons, so be sure to check local laws. Here are some general ranges by size.
| Septic Tank Size in Gallons | Average Cost for Tank Only |
|---|---|
| 500 | $500–$900 |
| 750 | $750–$1,200 |
| 1,000 | $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. On average, you can expect to pay $1,000 to $5,000 for leach field installation, with a field for smaller tanks costing on the lower end of that range.
Excavation
Excavation costs should be included as part of your quote. You’re likely to pay anywhere from $200 to $1,800 for excavation. Tanks that are closer to 500 gallons need less land excavated, therefore decreasing the overall cost for this task.
Perc Test
A perc test will 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.
How Much Does a Small Septic System Cost by Type?
There are three main types of septic tanks: concrete, plastic, 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.
| Material | 750-Gallon Average Cost | 1,000-Gallon Average Cost |
|---|---|---|
| Concrete | $2,860–$13,900 | $3,830–$18,600 |
| Plastic | $2,660–$13,900 | $3,630–$18,600 |
| Fiberglass | $3,360–$13,900 | $4,330–$18,300 |
If you’re still unsure on which material to go with, below are pros and cons across concrete, plastic, and fiberglass.
| Concrete | Plastic (PVC) | Fiberglass |
|---|---|---|
| Long-lasting (up to 40 years) | Long-lasting (up to 50 years) | Mid-range life span (20 to 30 years) |
| Approved for use in every state | Budget-friendly | Least costly |
| Not easily damaged | Lightweight | Stronger than plastic |
| Less prone to rust | Less prone to cracking | Won’t rust |
| More costly | Easy to damage during install | May shift depending on soil conditions |
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 cost 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
How Angi Gets Its Cost Data
Home is the most important place on earth, which is why Angi has helped more than 150 million homeowners transform their houses into homes they adore. To help homeowners with their next project, Angi provides readers with the most accurate cost data and upholds strict editorial standards. We extensively research project costs to develop the pricing data you see, so you can make the best decisions for you and your home. We rely on reputable sources, including the U.S. Bureau of Labor Statistics, academic journals, market studies, and interviews with industry experts—all to ensure our prices reflect real-world projects.
Want to help us improve our cost data? Send us a recent project quote to [email protected]. Quotes and personal information will not be shared publicly.
Frequently Asked Questions
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.
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.
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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