How much will your septic system installation or replacement cost?

Ashburn, VA 20149

Septic System Specialists on Thumbtack cost$500 - $5000

National average fixed price

  • Lowest price:$0
  • Most common low price:$500
  • Most common high price:$5000
  • Highest price:$0

How much does a septic tank cost?

National average costs range from $500 to $5,000. The national average costs for a septic tank installation or to replace aging septic system depend on several factors.

Septic Tank Installation Average Costs
National Minimum Cost $500
National Maximum Cost $5000
National Average Cost $1500

One in five homes in the United States relies on a septic system for wastewater management, according to the Environmental Protection Agency (EPA). If you use a septic system, it may be for your individual house, or you may be plugged into a community septic system that serves a small group of properties. A septic system is an on-site treatment system for the wastewater generated by a home or business. Sewage lines carry wastewater from your shower, toilet, sinks, clothes washer and garbage disposal out of the house and into a septic tank buried in the yard. In the septic tank, the heavier solids separate from the floatable matter and the remaining liquid drains out from the tank through a series of perforated tubes into a drain field or leach field. As the liquid filters down through the soil, dangerous bacteria is removed, making the water safe once more.

Septic systems are commonly used in rural areas that do not have a centralized city sewer system. Septic systems can be installed during new construction of a home or building, or they can be replaced by removing an existing tank and installing a new one. Tank capacity ranges from under 1,000 gallons to 2,000 gallons or more, with the amount of water you use on a daily basis determining the size of tank you need. Homeowners can either provide the materials for a new septic system themselves or ask a septic system professional to provide them. Septic system installation or replacement is available for condos, apartments, homes, commercial spaces and other buildings.

What's in this cost guide?

Soil type

The accessibility of the current septic tank or the site of the new system affects the cost of installation. For example, if the proposed site is under a concrete driveway, that driveway may need to be demolished and removed, which will add to overall costs. If the workers must navigate around a large tree with an extensive root system, costs will also likely increase. Extremely rocky soil can also affect cost, as can overly wet soil or other adverse soil conditions. The longer the crew and an engineer needs to be onsite preparing your land for installation, the higher your costs will be.

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Tank size and tank type

Residential septic tanks typically range in size from 800 to 1,300 gallons with most people opting for a 1,000 gallon tank. According to Milan and Son Plumbing in Deerfield Beach, Florida, this size is good for an average two- to four-bedroom home. The price of septic tanks increases with the holding capacity of the tank. A two-bedroom house can meet its needs with an 800-gallon tank because the household has less wastewater to process on a daily basis than a four-bedroom home, which might need a 1,200- or 1,300-gallon tank. Septic tanks continually self-clean, so getting a bigger tank doesn't mean homeowners can avoid maintenance for longer. Don't buy a 3,000-gallon tank for your condo thinking you won't have to take care of the system as often.

Tanks may be made of concrete or plastic. Plastic tanks are less expensive than concrete tanks and are easier to move and install. However, plastic septic tanks are not authorized for use in all states and, disturbingly, can rise up to the surface of the soil if not properly installed. The septic tank you choose is a critical part of your home water system, so don't base your decision on price alone. Do your research and take advice from the professionals about the best tank size and type for your household needs. Here are some examples of the average cost of septic tanks:

  • Plastic septic tanks, ranging in size from 750 gallons to 1,500 gallons: $500-$1,500
  • Concrete septic tanks ranging from 750 gallons to 3,000 gallons: $1,300-$5,000


In addition to expert knowledge of code and installation techniques, plumbing companies that install septic systems need heavy machinery when working with concrete tanks. Milan and Son Plumbing has a backhoe tractor that crews use to prepare the earth and dig the hole at the installation site. An average concrete septic tank can weigh 8,000-12,000 pounds, depending on gallon capacity. Milan and Son Plumbing secures the tank to the backhoe, carries it to the installation site and lowers it into the ground. According to Milan and Son Plumbing, there are many variables to a proper installation. The ground at the base must be level, and if the tank is not installed correctly the first time, it must be repositioned. If it rains during installation, the wet ground can pop a tank out of place and it will have to be reinstalled. Installation costs often depend on the business and operating costs of owning an $80,000 (or more) backhoe tractor.


Installing a new system or replacing an existing system can take two to five days for a local contractor to complete — usually three days on a typical job. Wet weather, extenuating soil circumstances (such as tree roots) or site inaccessibility can extend the installation by a few days. Prices for installation vary depending on the type of septic tank (concrete or plastic), the size of the tank, the cost of labor in the region and any additional prep work that must be done to prepare the ground for installation. Milan and Son Plumbing charges an average of $9,000 to remove an old tank and install a new system. Some jobs have cost as much as $12,000 because of problems at the site such as tree roots.

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The EPA recommends that property owners have their septic tank pumped every three to five years. A licensed plumber can pump out the tank without having to remove it from the ground. According to the EPA, "If the bottom of the scum layer is within six inches of the bottom of the [tank] outlet or if the top of the sludge layer is within 12 inches of the outlet, your tank needs to be pumped." Milan and Son Plumbing charges $300-$500 to pump a septic tank.

Lift station

In some cases, the house or septic tank is lower than the drain field and a lift station is required. A lift station is a type of pump that kicks on when the waste in the tank reaches a set level. This mechanism ensures that wastewater continues to flow out of the tank and into the drain field, keeping the operating system working properly — regardless of gravity. "We see the need for more of these in the Miami area, where the homes are lower in elevation than their backyards," say the experts at Milan and Son Plumbing. The company charges an additional $3,000-$5,000 to install a lift station.

Alternative septic systems

For steep sites, extremely rocky ground or bad soil, alternative systems work well. These include aerobic septic systems, mound septic systems, raised-bed septic systems and others. Depending on the location and type of system, costs may be higher or lower than the average septic system installation or replacement.

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How septic tanks work

A properly installed and well-maintained septic system keeps you, your family and your neighboring community safe. When a septic system fails, harmful — even dangerous — disease transmission can occur as contaminated water spreads through the soil and waterways. Understanding how your newly installed septic tank operates will help you keep it in good working condition. Here is how a septic tank system works, as outlined by the EPA:

  • When you shower, do laundry, flush the toilet, etc., used water runs through the pipes in your home to one main drainage pipe leaving your house, which flows out into a septic tank.
  • The septic tank is a buried, watertight container. Most often it is made of concrete, fiberglass, or polyethylene. The tank is made to hold the wastewater long enough to allow solids to settle to the bottom, forming sludge, while the oil and grease floats to the top as scum.
  • By design, compartments and a T-shaped outlet prevent the sludge and scum from leaving the tank and traveling into the drain field area.
  • The liquid wastewater (effluent), however, is able to exit from the tank out into the drain field.
  • The drain field is a shallow, covered, excavation made in unsaturated soil. Pretreated wastewater is discharged through piping onto porous surfaces that allow wastewater to filter through the soil. The soil accepts, treats and disperses wastewater as it percolates through the soil, ultimately discharging to groundwater.
  • If the drain field is overloaded with too much liquid, it will flood, causing sewage to flow to the ground surface or create backups in toilets and sinks.
  • Finally, the wastewater percolates into the soil, naturally removing harmful coliform bacteria, viruses and nutrients. Coliform bacteria is a group of bacteria predominantly inhabiting the intestines of humans or other warm-blooded animals. It is an indicator of human fecal contamination.

Signs you need a new system

No one wants sewage water bubbling up through their front yard during the hottest day of summer (or even on the coldest day of winter). Wastewater is not only stinky and gross, it's dangerous, carrying protozoa, bacteria (such as E. coli) and viruses that can be transmitted through fecal matter. If your septic system is leaking, overburdened or damaged, dirty wastewater can leach through the soil to contaminate the water you and your friends and neighbors drink. Whole communities can become ill if there is a major wastewater problem. Knowing what signs to look for can help prevent a problem before it begins. The first step to a happy septic system is proper maintenance, which includes having your septic tank pumped every three to five years by a professional. If your septic system is not regularly cleaned, it can clog and lead to failure.

Other signs can alert you that it's time to call your septic system professional ASAP to either repair or replace the system. The Washington State Department of Health says that red flags include water and sewage from your toilets, drains and sinks that is backing up into your home; drains in your bathtubs, showers and sinks that are draining too slowly; gurgling sounds in your plumbing system; pooling water or damp spots visible near or above the septic tank or drain field; a bad smell around the septic tank or drain field; suspiciously lush grass (from all that — ahem — fertilizer) over the septic tank or drain field, even during dry weather; algal blooms developing on nearby ponds or lakes; and high levels of nitrates or coliform bacteria (found in fecal matter) in your water well when you test it. There may be many reasons your septic system is failing, but, according to Washington State DOH, some common causes are clogged pipes running from the house to the tank, blockage to the inlet baffle to the tank, failure of the drain field, or a clogged outlet baffle or effluent filter.

How to hire a pro

A septic system is a big investment. And while fixing your septic system may not be as aesthetically pleasing as repainting your house or remodeling your kitchen, the joys of clean, healthy drinking water are impossible to beat. Because the cost of a septic tank and the installation process will run you into the thousands, it's important to do your due diligence when hiring a pro. Hiring an experienced and qualified professional can prevent major problems like system failure or your tank popping above ground, which can result from a poorly done installation.

When beginning your search, determine whether your state requires septic tank installers to have a contractor license. In California, a sanitation system contractor license is required to perform this type of work. Always check the contractor license number against the state database to ensure the contractor's license is valid and up to date, and that no formal complaints have been filed against them. You'll also want to check whether your regional government has any licensing requirements for this type of work. Next, read reviews! Find a company that has a solid background and has been in business long enough to give you the confidence that if something goes awry, they'll be around to fix it. Call up to three installation professionals to give you quotes, and have them provide a clearly written estimate that includes information on your tank size and type, details of the pipes and drainfield, and any other particulars. Never pay the pro in full upfront. Many require a deposit to begin. You will also want a clearly written contract that includes each detail of work, cost, installation information (depth and placement of tank, etc.), labor and product warranty, and projected completion date. Good communication will help ensure a positive experience.

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Pro tips:

  • Don't ignore warning signs, say the experts at Milan and Son Plumbing. Bubbling water in the sink, tub or toilet when you have a septic system can mean that it's backed up. It's better to have a pro check it out than to risk a backflow of sewage.
  • Be on the lookout for bad odors and wet spots on the surface above your tank or drain field. Better safe than sorry!
  • When hiring an installation pro, read client reviews and follow up with references to make sure you're choosing the right pro for your project. For more, check out our tips for smart hiring.
How do we know these prices?

Millions of people ask Thumbtack for help with their projects every year. We track the estimates they get from local professionals, conduct our own research and then we share those prices with you. The prices reflected in the article above are for informational purposes only and are subject to change at any time. Contact a professional near you to receive a personalized cost estimate for your project.


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