How Much Do Septic Tanks Cost?

Expect to pay at least a few thousand dollars to replace or install a septic tank or entire septic system.

U.S. News & World Report

How Much Do Septic Tanks Cost?

Septic tank underground waste treatment system

The national average cost for a septic tank installation is about $6,000, according to HomeAdvisor.(Getty Images)

If your home isn’t hooked up to a municipal sewer system, your alternative is a septic system, which includes a container buried underground on your property that holds and treats the water and waste that leaves your home via plumbing pipes.

Whether you’re looking to install a septic system as part of a new construction home or to replace an old septic system, septic tanks should be installed by professionals only. The complexity and scale of the project requires heavy machinery, careful digging and plumbing hookups that could prove disastrous if done incorrectly.

Septic tank installation requires initial ground tests to ensure the soil is suitable to hold a septic tank. Properties where the ground floods often, for example, would face frequent septic problems. Depending on where you live, you’ll likely need a permit to move forward with the installation, and an engineer will need to design the system including the tank’s placement and the location of the drain field, which is where water is allowed to leave the septic tank and be absorbed into the soil.

A contractor must then dig in the area of the tank and drain field for installation, which includes plumbing hookups to the home. Throughout the process and upon completion, the system will likely need to be inspected and approved for the permitting process to be complete.

From beginning to end, installing a septic system requires detailed planning, the expertise of a professional and at least a few thousand dollars to get the job done right. Here’s what you need to know about the cost to install and maintain a septic tank.

How Much Do Septic Tanks Cost?

The national average cost for a septic tank installation is $6,037, according to home improvement information site and network HomeAdvisor.

If you’re replacing your septic tank or system, this cost is in addition to any repair attempts you may have already made. Keep in mind that the old tank will need to be removed as well, which will either be worked into the total cost of installation or considered a separate cost by the septic system contractor.

“If problems get to the point where an entire septic system must be replaced, the costs can range from $3,000 to $10,000,” says Glenn Gallas, vice president of operations for Mr. Rooter Plumbing, a national plumbing company based in Waco, Texas.

Depending on the size and location of your home, as well as the size and material of your tank and your preferred type of septic system, you may find yourself paying even more. HomeAdvisor reports that aerobic septic systems, which use oxygen-loving bacteria to break down waste and require an air pump and more than one tank, can cost up to $20,000 to install.

A septic tank can be made of four types of material:

  • Concrete. This is the most common septic tank material and can last decades, but is prone to cracking.
  • Plastic. A less expensive material, plastic is lightweight and can lead to structural damage.
  • Fiberglass. The light weight of fiberglass means it can sustain structural damage or shift from its position, but it’s less likely to crack.
  • Steel. Steel can rust and the cover may corrode over time, which becomes a safety hazard in your yard. Steel is the least popular material used today.

You’ll also need to know how big your septic tank should be, which is based on the size of your house:

  • 750-gallon tank for a home under 1,500 square feet, one or two bedrooms.
  • 1,000-gallon tank for a home under 2,500 square feet, three bedrooms.
  • 1,250-gallon septic tank for a home between 3,500 and 4,500 square feet, four or five bedrooms.

For a septic tank under 1,000 gallons, the tank itself will likely cost between $600 and $1,000, according to HomeAdvisor, while a tank that's 1,200 gallons or more is more likely to cost $1,200 to $1,600.

The amount of time it takes to install a septic tank varies based on the weather, type of soil and other factors. Heavy rains that saturate the soil will delay an installation, says Michael DeCosta, director of branch operations for mergers and acquisitions for Wind River Environmental, a mechanical systems contracting company that installs and repairs septic tanks, among other specialties. Rocky ground can slow the process, making it last a week or more. On the other side, "You go to Florida, you go to Cape Cod where there's a lot of sand, those installs are a day," says DeCosta, who is based in the Boston area.

How to Get an Installation Cost Estimate

Before you contact a septic system installer, you'll need to check with your local governing body, such as the city or county, to see what is required to obtain a permit for the installation.

In many places, the local planning board or board of health will have a list of licensed engineers to choose from to design a septic system, DeCosta says. The engineer's plans, which take into account the water table, underground water lines, wells and required setbacks from neighbors' property lines, will then go before the local governing board for approval.

"Once any plans are approved, then you can take the plans and give them to different septic installers for pricing and guidance," DeCosta says.

The total cost of your septic system installation varies based on your house, the size of your property, nearest floodplain, soil, preferred tank material and myriad other details. To find out the true cost of your installation, you’ll need to get an estimate. A septic installation professional will likely want to visit your property, take measurements and examine any issues if you’re looking to replace any part of your current septic system.

Reach out to multiple local septic installation or replacement companies to get a few estimates based on the details of your home. While multiple professional visits for estimates may seem like a lot, the knowledge you gain from each conversation can help you decide which company offers the best materials and timeline for you – not just which company offers the lowest price.

Additional Septic System Components

There are other parts of a septic system you may need to include if you’re installing a new system or replacing an old one. Here are some of the components that make up the total cost of a septic system installation or add to the cost of replacing a tank:

  • Sewer line.
  • Distribution box.
  • Field lines.
  • Drain field or leach field.
  • Baffle.
  • Tank pump.
  • Tank lid.
  • Risers.
  • Tank tee.

Gallas explains that the sewer line, septic tank, distribution box and field lines can be replaced separately if only one or two components appear to be causing the issue. But if the system overall is having significant issues, replacing only one part “is like putting new tires on a car when the engine is about to quit,” Gallas says.

The Cost of Maintaining or Repairing Your Septic Tank

With proper maintenance, a septic system can last as long as 25 or 30 years for a home, according to Gallas. Maintenance is key, however, because small issues can build up over time and cause larger problems.

You will occasionally need your septic tank pumped, in addition to other maintenance, and Gallas says the frequency depends on the size of your house. Some experts recommend that a home septic be pumped every three to five years. A routine septic pump by a professional can range between $100 and $300, Gallas says.

If you notice issues with your plumbing or experience water backing up into the home, call a plumber to diagnose the issue. It may be a matter of a clogged pipe, but it could also indicate a problem with your drain field, a cracked or damaged septic tank, excess water in the tank or items and chemicals in your septic tank that should not have gone down the drain. HomeAdvisor reports that a plumber costs, on average, between $45 and $200 per hour, depending on where you live.

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