Installing a new septic system is expensive. On average, a typical installation will cost between $3200 and $5000 for a 3 or 4 bedroom home. However, that cost varies widely due to a number of factors, such as system size, tank material, site conditions, land clearance needs, and labor costs.
Let’s break down the numbers a bit further to identify why the costs vary.
Septic system installation costs depend on the size of the system being installed. The size of your septic tank depends on the home’s square footage and how many bedrooms it has. Tank sizes can start as small as 500 gallons for a one-bedroom home and go up to 1500 gallons or higher for a home with five or more bedrooms.
A polyethylene 750-gallon tank for a one or two bedroom home costs around $1200. A fiberglass 1500-gallon tank for a five or six bedroom home costs around $2660. The prices include basic excavation, placing the tank, installing the inlet and outlet, and back filling after the final hookup.
Septic Tank System Design
Septic tanks have a variety of designs to fit a number of site and condition requirements. The design plays a role in how much the entire system costs.
- Conventional/Anaerobic – A conventional septic system uses gravity to drain the waste into the septic tank, then out into the drain field. This design is the easiest and cheapest to install.
- Aerobic – Aerobic septic systems use a motorized pump to draw oxygen into the system, helping the effluent to break down faster. It requires a smaller drain field. However, the motor and timer, as well as the specialized installation, does drive the cost up significantly.
- Above-ground – Some soil conditions don’t allow for a conventional drain field. The soil may be completely impermeable, too permeable, sitting on top of bedrock, or have groundwater too close to the surface. An above-ground, or mound, septic system requires specialized engineering. It is one of the most expensive options for septic systems.
- Sand Filter – In areas where the groundwater is high, a sand filter septic system may be an option. A pump draws the effluent up so that it can filter down through boxes filled with sand. The sand removes a lot of contaminants before it distributes out through a drain field.
- Pressure Distribution – When the groundwater is extremely high, a pressure distribution septic system offers a solution. A pump pushes the effluent out over a wider drain field that gravity-fed cannot reach. It costs more than a conventional system, but less than an above-ground option.
The material used in the tank construction also plays a part in how much your system will cost. Plastic, fiberglass, and concrete are the most common materials used today.
Concrete septic systems are durable and can last 30 years or more. The typical cost for a 1500-gallon concrete tank ranges from $1100 to $1520. You can get models reinforced with rebar, which helps prevent premature cracking or deterioration.
Fiberglass tanks are lighter than concrete and easier to install. They don’t deteriorate underground like concrete eventually will. A 1500-gallon fiberglass tank will cost around $1975.
Plastic tanks are cheaper than concrete and just as easy to install. They don’t tend to crack, but they can break under pressure. Some jurisdictions do not allow plastic tanks in septic systems. The average cost for a 1500-gallon plastic tank ranges from $1270 to $1900.
Other Factors to Consider
When installing a septic system, you need to consider a few other things.
- Permit costs
- Soil testing
- Land clearance
- System design
- Leach field installation
- Inspection and testing
- Landscaping costs
With so many factors to consider, figuring out the cost of a new septic system can be overwhelming. Getting professional estimates from multiple septic companies is an ideal way to figure out the cost for your particular home.