Septic Tank Cost in 2021 [Installation Costs & Replacement]

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To estimate the tank size you need, multiply the number of bedrooms in your home by 150 and then multiply that by two. For example, if you have a two-bedroom house

Septic systems are a necessary portion of rural living. Where there are not any important sewers, they deal with the wastewater discharge from your home.

There are dozen of sorts of septic systems ranging in cost from $1600 to $14,000 — most homeowners spend $5900–$8300 to install a 1000-gallon tank plus a drain field suitable for a 2–3 bedroom home.

How Much Does it Cost to Install Septic Tank System In 2021?

The average cost to install a new septic system will run you about $7125.00 for a complete septic tank system, including a tank, drainage pipes and drain field. Small, simple set-ups with no installation challenges could run as little at $4200 installed while systems for a large home with unique landscaping considerations could exceed $14000. Prices vary by size, materials and design.

Septic System Cost By Tank Size

Septic systems are required by code to handle the amount of effluent your home produces. If an undersized tank overflows, sewage could back up into your house or contaminate local groundwater. Tanks range in capacity from as small as 500 gallons to 2000 gallons or more — 1000-1500 is suitable for most homes.

To estimate the tank size you need, multiply the number of bedrooms in your home by 150 and then multiply that by two. For example, if you have a two-bedroom house, you’ll need a minimum of a 600-gallon tank. Most municipalities require at least a 1000-gallon tank to accommodate the additional wastewater produced by modern appliances and bathroom fixtures from dishwashers to walk-in tubs.

 

Prices vary by tank material.                                           Septic system by the gallon cost
500-gallon                                                                                     500–$800
750-gallon                                                                                 $800–$1250
1000-gallon                                                                               $1200–$2200
1250-gallon                                                                               $2000–$2500
1500-gallon                                                                               $2200–$2700

Septic System Cost by Home Size

Septic professionals also estimate system costs by home size based on the number of bedrooms and corresponding baths.

Cost of a Septic System for a 2-Bedroom House

Small 1- and 2-bedroom homes could use tanks less than 1000-gallons, but most towns require at least 1,000 to future-proof the system. The good news is that by installing a slightly oversized tank, you can add another bedroom or bathroom without upgrading the system. Prices range from $2200–$4200 — most homeowners invest $3900.

Cost of a Septic System for a 3-Bedroom House

The average 3-bedroom house also requires a 1,000-gallon septic system averaging from $2200 –$4200, but families with higher-than-average wastewater production should consider a 1250-gallon tank for about 10% more. Your septic professional will evaluate your usage requirements and make recommendations. Expect to pay an average of $3900–$4100 on average.

Cost of a Septic System for a 4-Bedroom House

Experts recommend a 1,250-gallon septic tank for houses with 4-5 bedrooms. Costs range from $2,400 to $5600. The average price is $4,100.
In general, tank size is chosen based on the maximum amount of effluent expected over the two-days it takes to process it — and because tanks are self-cleaning, buying an oversized model won’t reduce the need for regular cleaning and maintenance.

Septic Tank Cost by Material

Septic tanks come in a variety of materials, including stainless steel, plastic, concrete and fiberglass. Each has its pros and cons, including price.

Stainless Steel

Steel is typically synonymous with durability, but that’s not the case with septic tanks. Popular in the 1950s and ‘60s, metal tanks are less durable than those made with other materials because of their vulnerability to moisture, tree roots and soil acidity.

At an average cost of $500–$2500, steel tanks are among the least expensive, and when properly maintained, they may last up to 20 years. But because they can rust and perforate faster than expected, they’ve been phased out with few exceptions, such as temporary use, to avoid groundwater contamination.

Plastic

Polyethylene plastic septic tanks are lightweight and easy to install. At an average of $600 –$1800, they’re popular because they’re economical. But they’re less prone to cracking than concrete tanks; they can warp under pressure or in changing soil conditions, causing contamination if it affects the lid. The use of plastic tanks is limited in some areas.

Concrete

Concrete septic tanks are the most common because they’re both durable and cost-effective at $800–$2200. They’re heavy, so you’ll pay a little more for installation — and lesser-quality models can crack over time — but better tanks can last 30 years or more.

Fiberglass

Fiberglass septic tanks are the most advanced and trouble-free, combining the lightweight properties of plastic with durability that exceeds concrete. At $1600–$2700, they cost up to 50% more but can last up to 50 years.

Septic Tank Installation Costs 2021

All septic systems share the same purpose — to collect, treat and safely dispose of wastewater from your home’s toilets, tubs and sinks — but because no two properties are alike, there is a wide range of designs that vary significantly by price.

Most systems use a conventional septic tank — so material costs are stable — it’s the way systems treat waste that differs. Conditions from soil type, tank location and the slope of your landscaping determine which kind of system you need. A septic professional can guide you.

Types of Septic Systems

There are two general categories for septic systems — conventional and alternative. Conventional systems include the basic gravity-fed systems most homeowners are familiar with and newer pressure distribution systems that use a pump to force wastewater into a drainage field.

Alternative systems include:

  • Aerobic systems
  • Drip irrigation systems
  • Mound septic systems
  • Constructed wetland systems
  • Intermittent sand filters
  • Recirculating sand filters
  • Evapotranspiration systems and unique proprietary systems not covered here

Conventional Septic System Cost

Standard septic systems use gravity alone to move effluent from your home, through the tank and out to the drain field. Waste digestion is anaerobic — it requires no oxygen.

Prices vary based on the size of the system and the tank material, but they’re the least complex to install — costs for an average system range from $2400 –$4900.

Pressure Distribution System Cost

Pressure distribution systems work like standard systems, but they use a pump to spread effluent through the drain field more evenly. Why is that important?

Standard gravity-fed systems require adequate natural drainage. If your soil tends to retain water or your drain field is shallow due to ledge, a pressure distribution system makes the most of it — improving your drain field’s efficacy and extending its service life.

The system uses two tanks — a conventional tank and a smaller version that houses the pump. The price of a 1000-gallon system ranges from $2800 – $5000 to install, but its efficiency offsets the higher cost.

Alternative Septic System Costs

Not all alternative septic systems cost more than conventional styles. The choice of systems usually depends on the quality, depth and drainage characteristics of your soil a well as the size of your house lot and the system’s location.

Aerobic Septic System Cost

Aerobic septic systems use two tanks plus mechanical aerators that add oxygen to the system. The purpose is to promote aerobic digestion of waste. At $10,000–$18,000 installed, these are the most expensive residential waste treatment systems to install. You’ll also pay more for regular maintenance plus the cost of electricity for moving parts; however, aerobic systems also have distinct advantages:

  • They’re small. Despite the redundant tanks, aerobic septic systems require very little space — drain fields are a fraction of the size of conventional systems, so they’re ideal where space is tight.
  • They produce less pollution. Treatment of fecal bacteria is complete, so nearby water supplies are a lower risk of contamination.
  • Designs are flexible. Because the flow of waste doesn’t depend on gravity, they can be installed in irregular locations.

Drip Irrigation Septic System Cost

Drip irrigation septic systems use multiple tanks plus pumps to release wastewater in small amounts. Because they treat waste thoroughly before discharging it, they’re ideal for homes near ecologically sensitive wetlands or in cities where there’s no hook up to a sewer.

Systems are complex and require two to three tanks plus a pump and an extensive network of drip tubing, but they’re also fully controllable — an LCD panel shows the system’s status. Expect to pay $8500 –$13,500 for the system installed.

Mound Septic System Cost

Mound septic systems use areas of elevated ground to filter waste when soil drainage is insufficient for a conventional drain field — they forces waste through additional layers of soil to ensure it’s clean when it reaches groundwater. The system itself is simple, but it requires two tanks, and installation is complex. Prices range from $9000–$15000 or more.

Sand Filter Septic System Cost

A sand filter septic system works like a conventional system, but it pumps effluent to a separate tank filled with sand for additional filtration before discharge. These systems help avoid groundwater contamination for homes with high water tables and cost between $5800 and $9600 to install.

Evapotranspiration Septic System Costs

Evapotranspiration septic systems are similar in construction to conventional systems, but effluent is discharged into a watertight, gravel-lined bed where heat and sunlight cause it to evaporate — it doesn’t leach into groundwater. Systems are cost-effective at $2500–$3500 installed, and they work in all soil conditions, but they require consistently dry and warm conditions, so they’re found mostly in the southwest.

Cost Factors to Install a Septic System

Cost considerations, in addition to the size and type of system you choose, also include:

  • Engineering — Septic systems require the input of an engineer at an average of $500–$650. Factors they consider when designing your system include:
  • Slope — conventional septic systems can’t be installed where land slopes more than 30 degrees.
  • Fill — native soil is required. The use of engineered fill may be prohibited or require a special permit.
  • Wetlands — drain fields can’t be designed to discharge into wetlands or waterways.
  • Drainage — how well your soil absorbs water — determined by soil testing — as well as external forces that could flood your system.

Plans for new systems cost the most and take up to three weeks to complete. You’ll pay a little less when replacing an existing system.

Soil Testing

To determine which type of septic system you need, engineers first do percolation, or perc, tests that show how well your soil absorbs liquid. New home sites may fail if it isn’t permeable enough to absorb discharge or if it’s so porous that water runs right through it before it’s adequately filtered.

Typical perc testing requires drilling two holes that simulate conditions for a septic system. It takes up to a day to do at an average price of $300–$1200. Costs depend on the complexity of the procedure based on local regulations.

So-called “deep hole” soil tests look at soil down to a depth of 10 feet to ensure there are no barriers to drainage such as rock or a high water table. Prices range from $900–$2000.

Permits and Inspections

Permits for septic tanks range from $50–$200. Most towns also require a post-installation inspection at the cost of $100–$200.

Land Clearing

An open area is required for both tank and drain field installation. For areas of a quarter-acre or less, expect to pay $800–$100 for light cleaning, including small tree and stump removal. Restoring your landscape to its original condition after installation adds $300–$600.

Septic System Upgrades

Upgrades to your septic system like these can make it more user- friendly:

  • Septic Tank Riser

Cleaning an underground septic tank requires digging a hole in your lawn unless it’s equipped with a riser. Risers are plastic or concrete extensions that sit atop the tank and offer easy access to the pumping port.

Not everyone wants a riser on their lawn — they’re not pretty — but they come highly recommended if you live in a harsh climate or hate the work of restoring sod after your tank is cleaned. Costs range from $70–$350 installed.

  • Tank Alarms

Select types of septic systems can be equipped with tank alarms. They work like floats in a toilet tank and can tell you if water has reached an unsafe level because of a blockage, allow you to alter your usage until the situation is corrected. Prices range from $85–$230 installed.

  • Lift Stations

If a septic tank is installed below the level of the drain field, a lift station can keep effluent flowing when gravity fails. Lift stations are pumps that kick in when water in the tank reaches a preset level. Installed, they add $2500–$5000 to the price of a system.

Cost to Install a Septic System Drain Field

The cost to install a drain field ranges from $1500 to $5000 or more. The process includes excavation, gravel fill and piping. Your final price depends on the depth of the field, the amount of gravel required, the length of pipe and disposal of unwanted soil.

Septic Tank Replacement Costs

The cost to replace a septic tank is only marginally less than installing one from scratch. In cases where the original system malfunctioned, you’ll need an engineer to troubleshoot issues — and changes in building cost may force you to upgrade.

In most cases, what you’ll save in upfront fees such as land clearing and soil testing is offset by the $650 – $1000 you’ll pay for removal of the old tank and drain pipes.

Septic Tank Price for Mobile Home

A septic system for a mobile home is no different than for any other residence — but if you ever want to move it, rolling it over the system could cause it to collapse. Tanks and drain fields should always be located far enough away to avoid the hazard, but that rarely adds to the cost of installation unless the lot is small and requires a system designed for small spaces.

Choosing a Septic System

A wide range of factors from soil quality and house size to local regulation help dictate the selection of a septic system; however, there usually remains some choice based on your preferences. What should you consider?

Your Budget

Stick with conventional systems whenever possible and choose materials with a favorable price point. Most families who install a new septic system today will have moved by the time it needs replacement, so consider how long you will be in your home before opting for high-end materials like a fiberglass tank that may not pay for themselves long-term.

Maintenance Needs

Some septic systems require significantly more maintenance than others. Aerobic systems, for example, are more efficient and environmentally friendly, but they tend to clog if they’re not meticulously maintained.

Conventional septic systems require cleaning once every three years or so — otherwise, you’ll rarely have to give them a second thought. It pays to consider how much time you want to spend maintaining a septic system before choosing one that needs constant attention.

Environmental Impact

For people who care deeply about the environment, a more efficient septic system that discharges cleaner water may be worth the extra cost even if it’s not necessary. If your home is in an ecologically sensitive area, the type of system required may come down to building code.

Frequently Asked Questions

How long does the average septic system last?

Estimates range from 20 years for systems with plastic tanks to 30 years or more for concrete or fiberglass. Drain fields on properties with marginal drainage may require replacement more often than the tank.

What are the signs that I need a new septic system?

Signs include:

  • A persistent odor of sewage in your home
  • Water bubbling in toilets and sinks
  • Excessive build-up of solid waste in your tank
  • Puddles of smelly standing water in the drain field or on the lawn around the septic tank

Because of the risk of groundwater contamination, the EPA recommends prompt action if you suspect a problem with your septic system.

How often does a septic tank need to be pumped out?

The EPA suggests pumping every 3–5 years. Cleaning too often can disrupt the balance of bacteria in the tank while waiting too long can contribute to blockages and tank damage. The average cost for pumping depends on the size of tank — budget $100–$-175 for small tanks, $175–$250 for average models and $500 or more for tanks over 2000 gallons.

What’s the cost of a septic tank for an RV?

Today’s RVs are self-contained — they have integrated pint-sized septic systems called blackwater tanks that meet most needs. They do, however, need to be emptied manually, and that’s a hassle for anyone staying in one place long-term where there is no waste disposal site. In that case, installing a small conventional septic system is convenient. Costs average $1600–$3000.

Choosing a Septic Tank Contractor

Choosing the right contractor to install your septic tank system is the first step in a stress-free process.

Consider these tips:

  • Work only with companies that are licensed, bonded and insured. If technicians accidentally damage your home or septic system during installation or the contractor can’t complete the work, it protects you from financial loss.
  • Seek 3–5 detailed estimates, and don’t accept bids that are unusually high or low without explanation. Low estimates may not include essential services such as cleanup and disposal of old materials.
  • If the installation is challenging, stick with an experienced contractor.
  • Ask for several references for work done within the last year.
  • Get any warranties in writing. Transferable warranties for major home improvement are a selling point at sale time.

Final Thoughts

Spending thousands on a septic system 2021 isn’t as rewarding as buying big-screen TV, but household wastewater contains bacteria that can contaminate groundwater and spread disease. A sound septic system is a must for your health.

External References 

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