How Much Does a Septic Tank Installation Cost? (2022)

How Much Does a Septic Tank Installation Cost? (2022)

What to Know About Septic Systems Costs Both New and Replacement

If you’re considering buying a home that neeDo you need to replace your septic system? Are you interested in understanding the costs of septic system replacement?

If you’re considering buying a home that needs a new septic tank system or getting a construction loan to build a new property, you might need to know a typical septic system’s cost.

The costs involved with buying such a system are significant as it requires a lot of work from your contractor.

Many factors affect typical septic system costs. Let’s take a look at the things you need to consider when installing a new septic system, along with replacing an existing one.

Septic Tank Cost: DIY vs. Hiring a Professional

Installing a septic tank system is no small task, but when municipal sewer systems are unavailable, it’s a task that’s perhaps unavoidable. While the costs to install a septic tank may seem high or complicated, it’s often a more cost-effective option to install a septic tank than trying to install sewer lines from the city, if that’s even an option.


Many homeowners are interested in doing a DIY septic tank installation to save money. There are a number of tasks that can easily be accomplished by homeowners. Coordinating soil tests and obtaining proper permits are easy tasks. Homeowners can also remove existing landscaping features or dig the holes and trenches for the septic tank. Beyond these steps, it’s best to consider leaving the actual installation to a professional company that is licensed and insured in order to complete the job safely.

The stakes are high when installing a septic tank system since it’s the method of collecting and purifying infectious disease waste like E. coli. Improperly installing a septic tank could result in foul smells, contaminated water sources, and standing water on the property, all of which can put family and neighbors at risk. With qualified professionals doing the heavy lifting, homeowners can enjoy a smooth system that requires little effort to maintain. Once a septic tank company has been selected, homeowners can work with them to identify any tasks that can be done by the homeowner, if desired.

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Permits and Red Tape

Various tests will need to be undertaken before you can even consider having a septic tank installed. A deep hole percolation test, costing $1,500, determines the type of soil you have. A positive test means that you can have a standard leach field. A negative test means that you will have to have an above-ground or mound septic system, which will cost two or three times as much as a normal septic system.

Once the tank and system are fully installed, you will have to have them inspected. Permits cost approximately $300, with costs being determined by the area you live.

It’s also worth taking into account additional costs that might be incurred once the job is done. Expect to budget between $50 and $200 a year for maintenance, with pumping required every three to five years.

Finally, you may have to pay for landscaping and other work to make the area look good once the tank is installed and operational.

Image Credit: AuntSpray, Shutterstock
Image Credit: AuntSpray, Shutterstock

What Size Septic Tank Do You Need?

Septic tank size is typically determined by the number of bedrooms your home has. This is used as a way to estimate how much water will flow through the system daily. Generally, the larger the system, the higher the cost.

Two Bedrooms

A two-bedroom house requires a septic system with a minimum of a 750-gallon septic tank. However, in many municipalities, a 1,000-gallon tank is the smallest size allowed.

Three Bedrooms

A three-bedroom house will need a minimum of a 1,000-gallon water tank, which regularly handles about 360 gallons of water per day.

Four Bedrooms

A four-bedroom home requires a larger tank with a minimum volume of 1,250 gallons. It handles around 480 to 600 gallons of water per day.

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Types of Septic Systems and How to Choose the Right One

The role of a septic system is to safely transport wastewater from a property, back into the ground without polluting the ground water or introducing water pollution into nearby bodies of water.

Here we discuss how these treatment structures work, and how to choose the right one for your home’s size and site conditions.

How Do Septic Systems Work?

Septic systems function as below-ground wastewater treatment structures.  They are often used in rural areas that do not tie into municipal sewage treatment systems.

Combining natural processes with proven technology, these structures effectively treat waste water from residential plumbing such as kitchen sinks, bathrooms, washing machines and laundry drains.

Typical septic system components include a septic tank and a septic leach field design.

The function of a septic tank is to provide primary treatment and holding for waste solids, allowing them to be digested by organisms or to settle out in the tank bottom.

This wastewater treatment structure works by digesting organic components and separating solids and floatable components (such as grease and oils) from the waste water.

Traditional soil-based wastewater treatment structures release the liquid waste (or effluent) from the tank into a sequence of perforated pipes buried in a soil absorption area, chambers, or other types of technology that slowly release treated effluent back into the soil.

The function of a leach field is to efficiently disperse the liquid discharge (or effluent) from a septic tank to efficiently enable natural treatment of effluent within the soil before it enters the groundwater.

Typical Septic System Diagram

Types of Septic Systems

Types of Septic Systems

These are the features and benefits of the three types of subsurface waste water disposal structures:

Conventional Septic Systems – Anaerobic Systems

Traditional anaerobic septic systems with anaerobic bacteria treat wastewater without using oxygen. Up to 40 percent of the treatment occurs within the tank, and up to 70 percent occurs in a leach field.

This system requires a greater drain field footprint than an aerobic system. No electricity is required, nor is service required for the mechanical components.

The chambers of an anerobic unit must be pumped out by a professional every 3 to 4 years.

The cost to purchase, install, and maintain an anerobic septic system is typically less than an advanced treatment system. Depending on site conditions, the price can range from $1,000 to $3,000 for a conventional anaerobic septic tank.

Advanced Treatment Systems – Aerobic Treatment Unit Septic Systems

Aerobic septic systems (or advanced treatment systems) use oxygen to treat wastewater. Bacteria in aerobic wastewater treatment structures digest more organic solids than bacteria in anaerobic structures.  An aerobic septic system costs or advanced septic system cost, between $15,000 – $26,000.

This means that up to 90 percent of treatment occurs in an advanced treatment septic tank, while about 10 percent happens in a soil absorption field.

This aerobic process facilitates use of a smaller leach field (approximately half the size of a conventional system), because the released effluent is much cleaner.

This smaller size unit is ideal for properties on small lots or located near water.  Electricity is required, as well as service for mechanical parts such as the aerator.

It costs more to purchase and maintain an advanced treatment unit (ATU) than a conventional system.  Depending on site conditions, the price can range from $6,300 – $12,000 for an ATU system.

Alternative Septic Systems – Sand Filter Septic, Pressure Distribution Septic, and more

Alternative systems use pumps or gravity to enable septic tank effluent to trickle through sand, organic matter (peat and sawdust), constructed wetlands, or other media to remove or neutralize contaminants such as pathogens, phosphorus, nitrogen and more.

Alternative solutions can be designed to evaporate or disinfect effluent before it is discharged into soil.

New Septic System Installation Costs

There are two main types of septic systems, conventional and alternative, with those two categories breaking down further according to how the system manages waste. An alternative or aerobic septic system typically costs between $10,500 to $15,000 on average, whereas a conventional or anaerobic system ranges from $2,500 to $5,000 with most homeowners paying $3,500 on average.

 Septic System Types And Cost   Septic System Type

Septic System Types And Cost
Septic System Type Average Cost
Conventional Systems
Gravity or Anaerobic Systems $3,500
Pressure Distribution Systems $7,000 – $10,000
Alternative Systems
Aerobic Treatment Unit $10,500
Mound Septic System $15,000
Sand Filter Septic System $6,000 – $10,000

Conventional or Anaerobic Septic System Cost

Conventional or Anaerobic Septic System Cost

An anaerobic or conventional septic system costs $3,500 to install on average with most homeowners paying between $2,500 and $5,000. These are generally the quickest, easiest, and cheapest to install, and the effluent travels through the septic tank and on into the drain field using gravity.

Aerobic Septic System Cost

Aerobic septic systems generally cost $10,500 to $15,000 on average. The aerobic system breaks down the solids in the tank using oxygen, which is accomplished using a motor and a timer. The wastewater released is cleaner than that produced by conventional systems and can be used for above-ground irrigation needs after it’s 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.

Aerobic Septic System vs. Anaerobic

The main difference between aerobic and anaerobic septic systems are in how they treat the effluent. Anaerobic or gravity systems flow into a drain field while aerobic systems treat the effluent before it reaches the drain field with oxygen, biofilm in the drain tiles, or sand filters.

Mound Septic System Cost

The average cost for an above-ground mound septic system is $15,000, with annual maintenance costing as much as $500. It’s quite possible that the percolation test will come back saying that your soil isn’t of the right drainage quality to have an underground septic system, in which case you’ll have to install an above-ground septic system at two to three times the cost.

An engineered mound system is required when the soil type 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 Septic System Cost

A sand filter septic system costs between $6,000 and $10,000 to install on average. 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 drain field to protect the underlying water table. Sand filters have been known to have a useable life of up to 20 years in some locations.

Pressure Distribution Septic System Cost

Pressure distribution septic systems range in cost from $7,000 to $10,000 on average. They only require a distance of 2’ between the bottom of the system and the water table below, and they use a pump to get the effluent to reach more of the drain field that gravity can’t accomplish unaided.

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How much does it cost to replace a septic tank?

Expect to spend between $3,000 and $10,000 to replace the septic tank for a single-family home. However, this overall cost really depends on two other numbers: the price of your septic tank and the cost of installation.

Septic tank prices vary based on the type and size of the tank in question. The tank size you need is usually determined by the size of your household, so there’s not much choice there unless you want to go bigger to accommodate future growth.

On the other hand, you have more options when it comes to the type of tank you want:

  • Concrete tanks: A concrete tank can cost $700 to $2,000 before installation.
  • Fiberglass tanks: A fiberglass tank typically costs $1,200 to $2,000 before installation.
  • Polyethylene (plastic) tanks: A plastic tank is, on average, the most variable option at $500 to $2,500 before installation.

Steel tanks are also an option, but they’re less common and prone to rusting.

The Septic System Installation or Replacement Process

Here you’ll find everything you need to understand and oversee the installation or replacement of a quality wastewater disposal solution for your New Hampshire property.

How Much Does a Septic System Design Service Cost?

Installation of soil absorption field requires a septic system design service such as leach field design by a NH licensed Septic Designer.  The septic design cost of a septic system typically ranges from $1,500 – $2,000.  The price is determined by the scope of work that your specific property requires.

Your designer must make three key decisions.  These include whether to use a conventional (anaerobic) or aerobic (advanced treatment system); the type of drain field to use; and the type of septic tank to use.

He or she must evaluate and review existing property lines, perform a lot and soil survey, create a septic design and submit it with fees to local & state authorities.

The designer determines the best solution for your site by comparing the cost effectiveness and anticipated life expectancy of each system option, as well as accessibility for heavy equipment, lot topography, and site restrictions.

Other Key Factors in the Scope of Wastewater Disposal System Design include:

Septic system designer in test pit.

Septic system designer in test pit.

Location of Test Pit and Utilities – to mark areas to dig test pits in accordance with state and local setback regulations. Many towns require applications, fees, and scheduling with the town inspector. Test pits can be dug once they are staked and inspected, and Dig Safe has marked underground utilities if applicable.  (If the new system is installed immediately following the foundation-pour, underground utilities are not an issue.)

Coordination with Town Inspector – to schedule digging and inspection of test pits. A test pit must be large enough for the Designer to enter and observe the soil profile and characteristics.   Since test pits help identify the type and location of your subsurface wastewater disposal system, property owners are encouraged to be present for the testing, and any conversation with the inspector and project professionals.

Topographic Survey – is completed for an area of 75-ft to a 100-ft around the proposed Individual Subsurface Disposal System (ISDS), to determine relevant objects and elevations.

Septic Draft Plans – typically include test pit (soil survey) results, design objectives, system elements and specifications, a plan view, and other required lot information required by state and local authorities.

Preparation of Submittal Package – to include 3 sets of septic plans for the state (NH-DES), plus the number of sets your town requires, a stamped envelope addressed to NH-DES Subsurface Bureau (for your town to mail it directly to the state), and a state application form.  Some towns require a review of the plan, for a fee, before the plans are submitted to the state.  Most septic plans are processed by the state within 15 days; often much sooner, now that electronic permitting is commonly used.

As-built Plans – If any part of the plan changes, the designer is required to produce as-built plans before the state representative can perform an inspection prior to backfilling.

Project Scope Questions to Ask a Designer or Septic Professional

    • Does the quote include the price of mileage, drawings, delivery (mailed or in-person), etc.?
    • Will he or she be on-site, or available by phone for questions that arise in all stages of the process?
    • Is a Boundary Survey required? (Usually for tight lots; must be performed by a NH-Licensed Surveyor)
    • Are there any Wetland issues that require permits?
    • Is other site work required with individual subsurface disposal solution installation?

Septic vs Sewer Cost

A septic system costs $3,100 to $9,600 to install while connecting to a main sewer line can be slightly more affordable, around $1,500 to $8,000. Think of this system as your own personal sewage system. A septic system treats wastewater on site, with an underground tank and pipe system on your property. If your home plumbing system is not hooked up to a septic system, it is connected to the main city sewer line. Sewage connections carry the wastewater from your home and route it underground to a city or county treatment plant.

SystemCost (Installed)Sewer$1,500 - $8,000Septic$3

SystemCost (Installed)
Sewer$1,500 – $8,000
Septic$3,100 – $9,600

Cost to Install A Septic System for an RV

If you’re building a more permanent septic system for your RV, then prices are the same as installing one for a house at $3,300 and $5,000. An RV these days is generally understood to be a mobile vehicle. The septic system in an RV consists of a black water or wastewater tank, the contents of which are dumped into a sewer connection or dump station. It will need to be flushed, cleaned, and sanitized regularly to stay in good working order.

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What are the maintenance costs that add up for the septic system cost?

The septic system cost when you replace it is costly, but you can prevent future issues and catch problems early on with regular maintenance.

One of the biggest maintenance tasks related to septic systems is pumping. Over time, sediment and other materials build up in the bottom of your system. This material, called sludge, can’t travel through the pipes and created a thick coat in your tank. The more sludge in your tank, the less wastewater it can hold and the sludge will eventually block the pipes. By pumping your septic tank frequently, you can remove this sludge and keep everything moving. 

Septic tanks need to be pumped every three to five years. This costs about $400 on average. Pumping large tanks can cost $1,000 or more. If you have a small septic tank or a large family (that requires more wastewater) then you will likely need to pump your septic tank more frequently.  

Along with pumping every five years, you should schedule an inspection every one to three years. The inspector will check the sludge levels and check for issues with the system to see if repairs are needed.  

Before you balk at the cost of having a septic tank pumped, think about what could happen if you don’t maintain it. Not only will it cost thousands of dollars to replace it, but you could end up with sewage in undesirable places. You could experience backups in your toilets and sinks or have to contend with foul odors around your home and yard. 

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Types of Septic Tank Systems

The total cost of installing or replacing your septic tank is largely dependent on the type of system you choose. Here are some of the most common kinds of tanks:

Anaerobic Septic System

Anaerobic systems are a common choice for many homeowners because they don’t require additional power or chemicals. An anaerobic system contains bacteria that do not need oxygen to survive. The bacteria break down solid waste and the remaining liquid waste is piped out and distributed under the soil. The waste is naturally recycled as the water passes into the soil.

These systems cost about $2,000 to $5,000 to install.

Aerobic Septic System

Unlike anaerobic systems, aerobic systems use bacteria that do require oxygen to survive. Oxygen is pumped into the tank to activate the bacteria, which then feed on solid waste. Aerobic systems work well where the soil isn’t favorable for other systems and the groundwater table is high. It’s a good option for homes located near a body of water.

Aerobic systems are more expensive to install. Expect to pay between $10,000 and $20,000.

Gravity Septic System

A gravity septic system uses gravity for filtration and water flow. They need to be installed on a gentle slope to enable water flow without a pump.

Installation costs $1,500 to $4,000.

Conventional Septic System

The conventional septic system consists of a septic tank and a trench that acts as a drain field. The trench is constructed on stone or gravel and allows water to pass through. To prevent sand or dirt from contaminating the clean soil, geofabric is installed on top of the trench. A conventional septic system needs a large space to operate.

These systems cost between $2,000 and $5,000 to install.

Mound Septic System

If your groundwater is close to the surface, a mound septic system is the best choice. A sand mound is constructed on the septic system area to pump wastewater from the tank into the mound in small quantities. The sand then filters the water before it gets into the soil and groundwater. This design requires a lot of space.

They’re also expensive to install because a sand mound has to be constructed. Total cost ranges from $10,000 to $20,000.

Chamber Septic System

Chamber septic systems have recently become a popular choice. They’re similar to conventional systems, except plastic chambers are used in the drain field instead of gravel. These are easier to construct and have a smaller carbon footprint.

They cost $1,500 to $5,000 to install.

Replacement Costs

Although costs vary according to the size of the leach field, soils and costs of local permits, expect to pay between $5,000 and $20,000 for leach field replacement. It is the most expensive component of the septic system. While areas with naturally sandy soil allow good percolation, or “percing” of the wasterwater downward, clay soils hold water.

The price of replacing your leach field depends heavily on soil type, as the field does not need to be as large for porous soil conditions as it does for less porous soils. If the section of your property containing the leach field is inaccessible and trees or fencing must be removed, that will also add to your costs. You also will need to factor in the cost of replacing sod in the area or planting new grass seed after the work is done.


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