Costs of an Onsite Wastewater System

How much does a septic system cost in 2024?

There’s no simple answer — the cost of every single onsite treatment system is going to vary according to a number of factors. What we can tell you is this: as of 2024, HomeAdvisor.com, which aggregates home improvement and maintenance resources, lists the typical range of septic projects to cost between $3,484-$11,703.

The basic factors that HomeAdvisor identifies as driving the cost variations include the size, type, and material you need for the system. Be aware that these three key factors, as well as some others, can drive your costs up well beyond the upper end of that range.

Visit HomeAdvisor for a detailed breakdown of the ranges of costs for tank size, anaerobic vs. aerobic system tanks, types of alternative systems, material types, installation add-on costs, replacement costs, and more.

You can also get an estimate of the costs for your specific project’s needs, by entering information into their estimate tool. For the sake of accuracy and due diligence, it’s recommended to have at least 2-3 cost estimates before determining a final estimated price.

To find other septic professionals in your area, check NOWRA’s Septic Locator lookup tool. You’ll want to be able to list other septic professionals as references for your work, or to check the cost estimates with, when engaging with new potential clients. Networking is important!

So what do you do if you need help financing your septic project? Thankfully, there’s a number of resources available for assistance. You may want to visit the Financing page at the National Onsite Wastewater Recycling Association website — NOWRA has a long list of sites and organizations to visit for assistance, including the Environmental Protection Agency, the Department of Housing and Urban Development and the Department of Agriculture, and more.

Some other resources we would like to particularly recommend:

• The Rural Community Assistance Partnership (RCAP) provides technical assistance and support to rural communities across the country. Their Water and Wastewater Technical Assistance Program has a special focus area in onsite/decentralized wastewater. While RCAP’s national organization does not provide services directly, their regional offices can assist with coordinating help for your community. Contact RCAP here.
• The Financing Septic Systems module in the EPA’s Water Finance Clearinghouse. The module is for homeowners seeking information to support the operations and maintenance, repair, or new construction of septic systems.
• Septic at EPA — Along with a host of other septic-related information and resources, the EPA has funding sources listed by federal programs, individual states, and tribal communities.

Well Water Contamination from Septic Systems

Many homeowners who use a septic system to provide wastewater treatment for their home often get their drinking water from a private well. If the septic system is malfunctioning or happens to be located too close to a drinking water well, contaminants from the wastewater can end up in drinking water. Learn how to locate, operate, and maintain your septic system to protect nearby wells and preserve the groundwater. Your septic system could contaminate your drinking water well or a nearby well under certain conditions, so it is important to regularly test the drinking water from your well (once a year is recommended) and take corrective action as needed.

Water from your toilets, showers, and other appliances contains harmful bacteria, viruses, and nutrients that could make you sick if it were to enter your well without being properly treated first. Maintenance issues like a full or cracked septic tank or a plugged drainfield can cause untreated wastewater to enter the surface water or groundwater. 

According to U.S. EPA: "Filtering wastewater through the soil removes most bacteria and viruses (also known as pathogens) and some nutrients. While soil can treat many contaminants, it cannot remove all of them (e.g., medicines, some cleaning products, other potentially harmful chemicals). If untreated wastewater surfaces in the yard, wastewater may contaminate your drinking water through an unsecured well cap or cracks in the well casing. It’s important to avoid flushing medication and chemicals into your wastewater since it could contaminate your drinking water."

The contamination risk to your well is lower the farther apart the well and septic system are located, the deeper the well is placed (and if it is in bedrock or below a defined layer of silt or clay,) or when your septic system is pumped and serviced on a regular basis.

The contamination risk to your well is higher if the well is at a shallow depth and in permeable soil, if the groundwater flows from the septic system towards the well, if there are many homes on septic systems near the well, or if there is poor construction or maintenance of the well and/or septic system.

Of course, there are a number of factors that can contribute to well contamination, from human mistakes and interference to natural groundwater chemistry. This video from our sister site, PrivateWellClass.org, discusses the basic circumstances that can lead to contaminated well water, and the kinds of naturally occurring contaminants that can be found in private wells.

Prolong the Life of Your Septic System

Regular maintenance and pumping out your septic system will help to prevent costly repairs. However, there are daily precautions that can be taken to help a septic system function properly. 

To flush or not to flush
The only things that should be flushed down the toilet are wastewater and toilet paper. Disposing of sanitary products, paper towels, tissues, diapers, etc. will cause harm to the septic system and you will need more pump-outs.

Don't put food down your sink
Food waste, coffee grounds, fat, and grease will cause great harm to the septic tank. Instead of disposing your food down the sink, try a compost pile for any non-meat food waste.

Don't use a garbage disposal
The garbage disposal doesn't make it easier for the system to handle food, grease, and fat. If you are going to have a garbage disposal, you need to have a larger than normal tank with an effluent screen, and that you pump the system more frequently. 

Don't rinse toxic materials down the sink or toilet
Pouring disinfectants, oils, paint, drain clearing products, etc. down the drain can damage the septic system. If enough toxic material reaches the septic tank, the tank's function can be impaired. 

Reduce your water usage
Cutting back on water protects your septic system by reducing the load of wastewater that the system has to handle. If you repair all leaky faucets and toilets, install low-flow water fixtures, and turn the water off while brushing your teeth or shaving, it will save money on water bills and save your septic system in the long run.

Taking care of your septic system by following these precautions will extend the life of your septic system and reduce the number of costly repairs that need to be made down the line. 

Featured Webinar: Alternatives to Traditional Onsite Wastewater Systems

This hour-long webinar recording from the Rural Community Assistance Partnership (RCAP) focuses on alternatives and advancements in traditional onsite wastewater systems and their unique applications and uses, including constructed wetlands, cluster systems, package systems, mound systems, etc. 

Alternative/ Innovative Onsite Wastewater Treatment Options:

Constructed Wetlands: A form of secondary or tertiary wastewater treatment that can be used by large municipalities and single-family homes alike. It is an organic wastewater treatment system that mimics and improves the processes that help to purify water in the same way as naturally occurring wetlands. This option uses water, aquatic plants, naturally occurring microorganisms, and a filter bed (containing sand, soil, and gravel.) 

There are two types of constructed wetlands: Surface Flow and Subsurface Flow wetlands. Surface Flow wetlands resemble natural wetlands in looks and the way they provide treatment. They are more economical for large volumes of wastewater. Subsurface flow wetlands are the most common type of constructed wetlands to treat household wastewater onsite.

Cluster Systems (also known as Community Systems): A decentralized wastewater treatment system under common ownership and collects wastewater from two or more dwellings or buildings. Cluster systems convey wastewater to a treatment and dispersal system located near the dwellings. These can be as simple as a subsurface disposal field served by individual septic tanks, or as complex as a neighborhood collection treatment and disposal system. 

Cluster systems transport wastewater via alternative sewers to either a conventional treatment plant or a pre-treatment facility followed by soil absorption of the effluent. The advantages of a cluster system are the shared costs with installation and future maintenance, but the disadvantages are undefined ownership and making sure everyone involved observes their responsibilities.

Pressure Manifold System: Uses pressure to distribute effluent in a more even, measured dose. Good for overcoming limitations of distribution boxes. Level manifold systems for effluent to flow equally via gravity. Sloped manifold systems have lateral trenches at various elevations to ensure that all branches operate at equal pressures.

Low Pressure Dose System (LPD): An anaerobic septic system with addition of a pump tank. Advantages with this option are that it can be installed in heavy clay soils, and it reduces the amount of land area required by the drainfield. Disadvantages include potential infiltration by roots, clogging of drain hose by solids, and wastewater accumulation in the drainfield. This system is not a viable option if water table is detected.

Drip Distribution system: Provides effluent dispersal that can be used in many types of drainfields. This alternative disperses treated septic water over a greater surface area of land. It irrigates the field with long flexible tubing that maximizes the treatment of sewage and minimizes the risk of untreated wastewater flowing too quickly through the soil. No large mound of soil is needed. This option requires a large dose tank to accommodate the time dose delivery of wastewater to the drip absorption area. A potential disadvantage of this method is that it needs electrical power which comes with increased maintenance and extra expenses.

Chamber System: This alternative contains no gravel in the drainfield. Instead, the drainfield is made up of synthetic chambers with bases that are open to the ground to allow effluent to drain into surrounding soil. Advantages with this method are increased ease of delivery and construction, they offer a large wastewater treatment volume, and it's good for areas with high water tables. Disadvantages are that this option will be expensive to install if the site has lots of gravel and sand, and this system could pollute the water table if the soil in the area has a high absorption rate.

Evapo-transpiration System (ET): Provides onsite wastewater treatment and disposal. Can dispose of wastewater into the atmosphere through evaporation from the soil's surface and or transpiration by plants. This option offers flexibility with the combination of seepage and evaporation, has a low risk of groundwater contamination, and it can overcome site, soil, and geological limitations that may come up. It is not suitable where land space is limited, or the surface is irregular. This alternative is only useful in arid climates with adequate heat and sunlight (it can fail if it rains or snows too much.)

Mound System: Good for areas with a shallow soil depth, high water table, or shallow bedrock. This method requires substantial amounts of space and periodic maintenance. Trees must be removed or cut back, and sand must be brought in to build the mound. This alternative can be expensive to install. 

Sand Filter: Provides a high level of treatment for nutrients and is good for sites with high water tables or are close to water bodies. With this option, treated water can pass directly from the sand filter to the soil without needing to pass through a leach field. 

Traditional approaches to onsite wastewater treatment are useful in many circumstances, but innovative alternatives are often the best choice for any unique situations that may arise. The alternatives to conventional septic systems mentioned above allow for cost-effective, long-term solutions if a traditional septic system is causing water quality problems.

Can A Septic Tank Float?

As crazy as it might sound, the answer is yes: Septic tanks can float out of the ground. Any buried structure will float when empty if it weighs less than the water that displaces it. That means that when installing any sort of septic system in an area with a high water table and/or that is prone to flooding, you must conduct buoyancy tests and determine if the system will remain stable.

Dr. Sara Heger, instructor at the University of Minnesota’s Onsite Sewage Treatment Program, has broken down the calculation to determine tank stability at Onsite Installer. The basic steps are below, but Dr. Heger’s walk-through explains each step in detail and shows example calculations. You will need to know the individual weights of the following: the empty tank, the minimum amount of water and media in the tank, the soil directly above the tank, and the maximum volume of water that is displaced.

Here’s the calculation:

1. Calculate the weight of water displaced by the tank (buoyant force B).
2. Calculate or look up the weight of the tank (WT).
3. Calculate the weight of the water in the tank (WW).
4. Calculate the weight of the soil cover (WS).
5. Evaluation of net forces.

So if your calculations indicate that the tank will float, what do you do then? Thankfully, there are anti-floatation measures that can be added to the system design plans. Perhaps the most basic is to use concrete, which weighs 85 pounds per cubic foot and can be added into the design in a few different ways. Some fiberglass tanks may also have an anti-floatation lip built onto them.

It’s important to consider that any anti-floatation measure will increase stress forces on the tank, so the tanks must be able to withstand the extra force. Read more from Dr. Heger at Onsite Installer on anti-floatation.

If you ever do need to deal with a flooded septic system, whether the tank has emerged from the ground or not, refer here:

• “Faced with a Flooded Septic System?” also from Dr. Heger at Onsite Installer
• “Protecting a Septic System During and After a Flood” at WaterOperator.org
• Contact the Onsite Sewage Treatment Program at UMinn.

Medications & Your Septic System

Can taking some forms of medications harm a septic system? The short answer? Yes. Some chemicals from medications are not completely metabolized in your body and are expelled in your waste. These chemicals can disrupt the biological action in your tank and drainfield causing it to fill with solids more quickly. More solids in your tank means there is a higher risk of solids flowing into the drainfield leading to septic system failure. 

The best way to ensure your septic system stays healthy and functioning is to provide consistent maintenance and inspections. It is also very important not to flush any medications or household chemicals (antibacterial soaps, harsh cleaning chemicals, chlorine bleach, etc.) down your toilet or sinks. Septic tanks and drain fields depend on both anaerobic and aerobic bacteria to break down the organic waste and clean the water as it is released it into the soil for filtration.

Some steps to protect a costly failure and potential replacement are:

• Flush only body waste and toilet paper down the toilet
• Use minimal household chemicals for cleaning
• Avoid or use minimal amounts of chlorine bleach in your washing machine
• Have your tank pumped more frequently if someone in your household is taking chemotherapy or antibiotic medications for an extended period
• When your tank is pumped, ask your pumper to refill it with fresh water to dilute any residual medications
• Take excess and unwanted chemicals, cleaners, and medications to your local household hazardous waste or medication collection program

Businesses on Septic Systems

If a business is in an area that does not have a public sewer system, or, if the business will generate a higher flow of additional wastewater than a sewer system will be able to handle, a commercial septic system will be necessary. This type of system, also called a large-capacity septic system, is defined by the U.S. Environmental Protection Agency as "a septic system that receives solely sanitary waste from either multiple dwellings or a non-residential establishment that has the capacity to serve 20 or more people per day."

The wide variety of facility types that a large-capacity system could service include schools, religious institutions, office and commercial buildings, shopping malls, hotels, restaurants, convenience stores, and more. Unlike residential septic systems or non-residential systems serving fewer than 20 people per day, the EPA does regulate large-capacity systems in order to protect underground drinking water sources.

Fundamentally, though, a septic system on a business property works in much the same way as a residential system, just on a larger scale. To keep up with the higher volume of wastewater the system will be handling, large systems will require more frequent pumping, maintenance, and service to ensure they operate properly for as long as possible. Business owners managing water use so that the system is not overwhelmed will also help keep the system in good working order.

Again, similarly to residential systems but on a larger scale, the costs of both installation and operating large-capacity systems will vary widely based on the individual factors of the commercial location and performance needs for the system.  

There are some differences to keep in mind for large-capacity systems. While these systems still only handle sanitary waste (so no industrial waste allowed), there are still different types of wastes produced by commercial buildings that their large-capacity septic systems will need to be able to handle. So they’ll need additional design components — such as grease traps in restaurants to keep fats, oils, and greases (the notorious FOG!) from clogging up the plumbing — and more specialized maintenance and service.

Multiple types of septic systems can be used for a commercial installation. AAA Pumping Service recommends sand filter systems, pressure distribution systems, evapotranspiration absorption systems, and cluster systems as well-suited for commercial properties. (A cluster system would serve multiple nearby businesses/commercial properties).

Note: Mention of commercial entities who share educational information does not constitute an endorsement.

Additional Reading

• Large-Capacity Septic Systems | U.S. EPA
• Best Septic Systems for Your Commercial Property | AAA Pumping Service
• Five Facts About Commercial Septic Systems | Moon Site & Septic
• Five Things to Know About Commercial Septic Systems | World Construction Today
• “Design Concerns with Restaurants, Convenience Stores, and Commercial Waste” Presentation | Onsite Installer

Source Water Protection

Source water is untreated water from streams, rivers, lakes, or underground aquifers. It is used to provide public drinking water and it supplies private wells with water used for human consumption. In order to give water utilities and community members the information they need to decide how to protect drinking water sources, the Safe Drinking Water Act requires that the states develop EPA-approved programs to carry out assessments of all source waters in the state.

We have over 2,300 resources (and counting) on Source Water in our Documents Database that provide valuable information on this topic. You can search for resources like the Drinking Water Mapping Application to Protect Source Waters (DWMAPS), a guide to groundwater protection, a Ground Water Rule compliance manual for water systems and states, an FAQ on abandoned wells, a flowchart to help determine groundwater sources under the direct influence of surface water (GWUDI), and many other useful guides that will help you to deliver safe and clean water to utility customers. 

To access the wealth of knowledge on Source Water within our database just select "CATEGORY" in the dropdown then choose "Source Water." Once you make that selection, a second dropdown will appear where you can choose "HOST," “TYPE,” or “STATE” to narrow the search even further. If you have a specific search term in mind, use the “Keyword Filter” search bar on the right side of the screen.

This is part of our A-Z for Operators series.

Protecting a Septic System During and After a Flood

When a home or the area surrounding it floods, the septic system is at risk of becoming waterlogged. This could be from a leak in the lid, rising groundwater that enters into the system, or an over-saturated drainfield that can't properly drain. A flooded septic system may lead to sewage backing up into the home and cause serious problems for the homeowner. 

Septic tanks may not always experience damage just because there is flooding, but any existing leaks in the system will allow floodwater, silt, and debris to enter the system. This presents a big problem since the extra dirt and debris can cause clogging. Extra water entering the septic system can also cause the floating solids to rise up and plug the pipes. The U.S. Environmental Protection Agency has information on what to do after a flood to ensure your septic system is protected. Below we have summarized this information with a list of dos & don'ts:

Septic System Flooding Dos & Dont's

This video provides some additional tips for how to avoid septic tank flooding and what to do if your system does flood:

Following these tips will help septic system homeowners to be prepared in the event of a flood and protect the septic system from further damages. If you need more specific advice or assistance with your septic system, contact your local health department for a list of septic system contractors in your area.

Sanitary Sewer Overflows

Properly designed, operated, and maintained sanitary sewer systems are meant to collect and transport all of the sewage that flows into them from a community into a wastewater plant for treatment. Sanitary sewers are the things we flush, pour down drains, etc. There are regulations that say stormwater and sanitary sewers are to be completely separate, but in many older, large communities they run together and can overload a wastewater plant.

We have 810 resources (and counting) on Sanitary Sewers in our Documents Database that provide valuable information on this topic. You can search for documents about the development process for publicly owned treatment works (POTW), benefits of protecting your community from sanitary sewer overflows, how to develop a collection system maintenance program, combined sewer overflow management, and many other useful guides that will help you to deliver safe and clean water to utility customers. 

To access the wealth of knowledge on Sanitary Sewers within our database just select "CATEGORY" in the dropdown then choose "Sanitary Sewers." Once you make that selection, a second dropdown will appear where you can choose "HOST," “TYPE,” or “STATE” to narrow the search even further. If you have a specific search term in mind, use the “Keyword Filter” search bar on the right side of the screen.

This is part of our A-Z for Operators series.