Ashburn, VA

Average cost for a Septic Tank System ranges from
$3,000 – $15,000

The average cost for a septic tank system is $3,250. Hiring a septic tank system installer, you will likely spend between $3,000 – $15,000. The price of a septic tank system can vary greatly by region (and even by zip code). View our local septic tank system installers or get free estimates from pros near you.

How much does a septic tank system cost?

Author: Daniel W.
Millions of people ask HomeGuide for cost estimates every year. We track the estimates they get from local companies, then we share those prices with you.

Benefits Tests & Permits Design Conventional Alternative Installation Tips

When building a home, barndominium, log cabin, or placing a manufactured home on raw land that is not connected to a local municipality waste system, a septic system is your best option for sewage treatment. A traditional septic tank for a three-bedroom house will average around $3,250. For conventional systems, it might be possible to get a suitable system installed for under $5,000 in the Midwest, whereas in coastal areas, one could cost $10,000 or more. For an engineered system, the costs will average around $15,000.

This pricing guide covers:

Septic Tank System Benefits

With municipal sewage rates already between $45–$60/month in some cities, and with rates increasing as much as 6.1% in some, a septic system can end up saving you a considerable amount of money the longer you own it. If your property allows for, or needs, a septic system, you will pay somewhere between $75 to $200 every 2.5 to 3 years to dump out or de-sludge the tank, in addition to the initial cost associated with its construction.

Depending on the construction methods, materials used, and the soil conditions where the tank is placed, a concrete septic tank can last as long as 40 years, and beyond. Given that the average person will move 11.4 times in his or her lifetime, a septic tank install will probably outlast the average homeowner’s stay.

Septic Tank System Installation

Planning & Survey

Before anything can happen, the best place to start is to have a site survey and a soil percolation test done by an engineer or licensed septic system design professional. With the results of the survey and the test, the right system can be designed for that area, and then the required permits can be applied for.

The elements of focus from the survey that will determine the design include the topography, the estimated capacity—based on the size of the home to be built and available land, and any wells are nearby.

Percolation Test

The percolation test will reveal the type of soil in the area and what depths the different layers are at; how deep each layer is; and with the combination of layers, how well suited the area is to filter and drain from the system. The soil that the effluent from the tank will flow into has to have the right level of absorbance to filter effectively, and as such, if the tests reveal that it is heavier than either gravel or sandy soil, there could be issues. In addition, careful attention will be paid to the seasonal water flow in that area to ensure everything that should stays well underground.

Percolation (Perc) tests are typically carried out with a power auger, a posthole digger, or a backhoe, since it will allow the inspector the clearest opportunity to see the underlying soil. In working with existing knowledge of the soil in the area for the best assessment of the soil, it is not uncommon for the contractor to make 2 or 3 cuts into the earth at a depth of between 3 and 6 feet. The results will point the design either in the direction of a standard septic system or an engineered solution for your waste treatment.

Positive results from the survey and test will also allow you to get approval for the drain field (also called leach fields or leach drains)—the below-ground disposal that will filter, decontaminate, and treat the wastewater by anaerobic digestion as it comes out from your septic tank.


You’ll need your permit from local authorities allowing construction. It is usual to need a site plan: a scale diagram of your land which details the location of the house, outdoor elements (like a detached garage, any walkways, any swimming pools), and the location of the septic system. You can apply for the permit yourself or the contractor can include this in the quote. On average the permit will take about 1–2 weeks to secure, and costs include the inspection during construction and after it has been completed. Expect to pay about $250.

Sometimes the local governing authorities will either carry out the assessment of the water table and testing of the soil themselves, or they will point you in the direction of approved vendors in that space.

There are three possible outcomes from the testing that needs to be done:

Worst Case - The ground cannot support a drainfield.

Better - Testing reveals that conditions are poor, so an engineered system must be built.

Best - Ground conditions are suitable for septic drainfield.

Layman’s test

If you are looking at some raw land and want to get some initial idea about the suitability of the area for a septic system, you can perform a layman’s test before you spend any money. Assuming you have permission to go out on the land, locate a spot where you think the tank could go that would be outside the perimeter of the home and dig just below the surface topsoil. Take some of the lower layer of soil, and if you can shape that damp lower soil into a ribbon of 2” long and it maintains that shape, your soil might fail a percolation test. Be sure to test the soil before purchasing the land, especially if your only method of removing wastewater is with a septic system.

Professional percolation tests will cost somewhere between $350 and $1,100 depending on where the land is situated, the equipment needed to dig—based on the type of soil, and the amount of development going on in the area. It could take between 2–4 weeks to get the test done and the results back.

Septic Tank System Design and Costs

The results from the percolation tests will determine what type of system is required to service the waste needs for your home. From there, the engineer will create drawings that will include the following:

  1. Tank location
  2. Tank capacity
  3. If applicable, the location and capacity of any required pumps and their power supply
  4. Location of the drain field
  5. Dimensions of the drain field
  6. Sand and stone needed to fill the length, breadth, and depth of the drain field area
  7. Setup and dimensions for the perforated pipe that will dispense the effluent into the drainfield

While there are already many designs available off the shelf, for most homeowners, it will take an engineer to design a custom system to suit your home—based on variables like capacity, location of the water table, location of any nearby wells, soil type, land elevation and degree of slope, and the best suited drainfield.

The design of the septic system will generally take between 2–3 weeks to design and cost an average of $600, depending on your location and the complexity of the system.

Septic Tank Size

The size of the septic tank needed for your home is based on the home’s size in square feet and the number of bedrooms. Based on a formula, this results in an overall capacity that is measured in gallons that determines the size of tank it takes to treat the wastewater for that number of people.

Standard tank sizes usually start at 750 gallons for a one- to two-bedroom house under 1,500 sqft, and go up to 1,315 sqft for a six-bedroom house that is less than 5,500 sqft.

The four most common types of septic tank solutions are either:

  1. Plastic tanks
  2. Fiberglass tanks
  3. Metal (usually steel)
  4. Concrete tanks
Concrete tanks are the most common type used in the US because of their durability. If they are made well with quality materials, and maintained properly, they can last 20 or 30 years or more.

Because of the nature of concrete, they are prone to cracking over time if they are not well made or properly looked after. Despite the strength and durability associated with steel, metal septic tanks will eventually rust and collapse and will likely be outlasted by a neighbor’s concrete tank. Because of this, and increased regulations by local authorities, they are used less and less, and in many regions are likely only to be found in existing systems already installed.

There are two common types of septic system available for homeowners in the United States —a conventional system or an alternative system. Which type is suited to install for your home will be dependent on the surrounding soil around your home and the site itself, including topography.

Conventional Septic Tank Systems

Gravity Systems

Averaging around $3,500, these are generally the quickest, easiest, and cheapest to install, and the effluent travels through the septic tank and on into the drainfield using gravity.

Pressure Distribution Systems

These systems range in cost from around $7,000 and $10,000. They only require a distance of 2’ between the bottom of the system and the water table below, and are quickly becoming a choice for many homeowners, because they use a pump to get the effluent to reach more of the drainfield that gravity can’t accomplish unaided.

Alternative Septic Tank Systems

Aerobic Treatment Unit

These systems generally cost an average of $10,500. The aerobic system breaks down the solids in the tank using oxygen, which is accomplished using a motor and a timer. This is different to the anaerobic process found in conventional septic systems. As a result, the wastewater released is cleaner than that produced by conventional systems and can be used for above-ground irrigation needs after it is sterilized. Additional benefits include needing a drain field half the size of that of a conventional system, which allows for more placement options on your property.

Mound Septic System

The average cost for a mound septic system is $15,000, with annual maintenance costing as much as $500. An engineered mound system is required when the soil on the homeowner’s property is either too permeable or completely impermeable, or if there is only a shallow cover of soil over porous bedrock, or a high seasonal water table present. The purification and cleaning of the wastewater is accomplished through a biofilm present in perforated drain tiles. This slows down the water while purifying it before it reaches the water table below. As the name might imply, it will result in a raised surface or mound on your property.

Sand Filter System

Costing somewhere between $6,000 and $10,000, the sand filter system is like a conventional septic system but it uses a pump to distribute the effluent to a filter system—sand housed in either a concrete or a PVC-lined box—a grid of small pipes. The sand filter allows for prefiltering of the water before it reaches the drainfield to further protect the underlying water table. Sand filters have been known to have a useable life of up to 20 years in some locations.

Septic Tank Installation Cost

To install a new septic tank system, the contractors will:

  • Clear the land in the area designated by the site plan before digging a hole to place the tank into.
  • Create the mechanism for taking the wastewater from the house by installing pipes under the ground to the location of the septic tank.
  • Start digging the hole for the tank, working with the engineer’s plans to make sure the tank will be at the right depth—to ensure the angle of the waste pipe leaving the house is not too steep. When that angle is too steep, the flow of liquids and solids is off, causing solids to get lodged in the pipes. Additionally, the tank has to be at the right height so the overflow enters the soil at the right layer for final filtering.

It is usual for the contractor to have an inspection scheduled at this point to satisfy local permit requirements. After successfully passing the inspection, the contractor can move on to the drainfield construction.

At this point the contractor will:

  • Dig a hole for the filtration materials of gravel etc., and fill it to the depth detailed in the plans for each layer.
  • Install the pipe connecting the opposite side of the septic tank from the inlet pipe through the earth to the top of the drainfield, where perforated pipes will distribute the effluent water so it can filter through as it makes its way to the water table below.
  • Cover the pipes’ trenches.

Again, it will be inspected and approved by the relevant authorities. When approved the drainfield will be covered over by the dirt removed while digging the holes, and, finally, the inspector can test the system. Once complete, the septic system will have a final inspection and testing performed.

From start to finish, the entire project could take up to three weeks or longer, depending on the permit processing and the complexity of the system you need for your property.

Septic Tank Pumping Cost

$75 –$900 | Average $370 | Every 3 years

If you live in a more rural location with no municipal sewage services available, you have to have an onsite septic system in place to take care of the wastewater from your house. Most tanks store three years’ worth of a home’s wastewater before they are due to be emptied/pumped.

Septic Tank Pumping

Looking for more details? We wrote the book on Septic Tank Pumping Cost, check it out here.

Selecting your contractor to install the septic system

To work toward making a final selection on your contractor, first create a list that contains the 3–5 contractors who fit most of the requirements on your checklist.

Try to find as many as possible who match the following criteria:

  • Have technicians with years of on-the-job experience
  • Offer a guarantee or warranty
  • Are A+ rated with the Better Business Bureau
  • Are bonded and insured.

Bowen's Plumbing & Septic Tank Service in Conyers, GA, who have been operating for 76 years, recommend that you get the entire cost quoted upfront.

Be sure to never pay the full amount upfront, however, down payments are common.

Once you have a detailed bid from all of them, you will be better equipped to move forward with your septic tank purchase and installation.

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