How Much Does a Septic System Cost?

This is a question that can vary drastically depending on the site conditions and what is allowable based off of what regulations are in place in the area you are building the system. Each set of regulations will determine how much a septic system will cost. Factors such as size of area of infiltration and soil depth / type play a deciding role in determining how much a system will cost. There are generally 4 types of systems that are commonly installed for residential use:

Type 1 Gravity System ($15,000-$20,000):

This type of system uses gravity to trickle effluent from the septic tank to the dispersal field. 3-4" perforated pipes are used in the dispersal field to release the effluent into the ground. Generally, a greater vertical separation and a faster percolating soil is conducive to a type 1 gravity fed system. In our opinion, gravity systems should be avoided at all costs due to the progressive failure effect. Because the systems are gravity fed, as soon as the effluent reaches the first (closest) hole in the pipe, it will drain out of there. Once the area underneath the first hole has become fully saturated, the effluent moves to the next and so on and so forth. this means the effluent is getting uneven distribution in the dispersal field and leads to the system failing over time. The typical cost for a type 1 gravity system is $15,000-$20,000.

Type 1 Gravity Drain Field

Type 1 Pressure System ($20,000-$25,000):

A Type 1 Pressure System must meet or have similar soil structure to that described in the above gravity example as this is still type 1 effluent with no treatment occurring at the tank or in the field. A pressure system is a much better system and preferred by professionals due to each pipe being completely filled with effluent (even distribution) and allowing the effluent to utilize the whole area of infiltrative surface. It achieves this by using an effluent pump which sends the effluent (wastewater) to the field. By using a pressured system, you extend the longevity of the system drastically compared to a gravity fed field. A type 1 pressure system ranges between $20,000 - $25,000.

Type 1 Pressure Drain field

Type 2 Pressure System ($25,000-$40,000):

A Type 2 Pressure system utilizes an effluent pump just like the above example and also treats the effluent before it is put into the ground. This can occur at the tank itself in the form of a treatment plant such as an aerator or a specialized suspended object in the septic tank that promotes bacteria growth. These systems work well for areas that are limited in size, or do not have proper vertical separation in the natural soils. A typical type 2 pressure system can cost anywhere from $25,000 - $40,000 depending on treatment package used and the size of the system.

Type 2 Pressure System

Type 3 Engineered System ($30,000-$60,000):

A Type 3 Engineered system can only be designed and planned by an engineer. A type 3 system usually consists of an extra element of treating the effluent before it goes to the dispersal field due to the lack of soils and or the size constraints of the system. UV lights are a common type 3 treatment system which produces a lower amount of Biological Oxygen Demand and Total Suspended Solids in the effluent. An engineered system can cost anywhere from $30,000 - $60,000, depending on what type of treatment plant is installed and how large the system is.

UV Light Septic Treatment Plant

At the end of the day, site constraints are going to dictate how much a septic system will cost. This is dependant on the size of the site, the soil assessment and the site assessment taking into account natural bodies of water, drinking wells, property lines & ground water. When a professional is designing a system, they generally cannot move backwards system to system. Meaning that, if your site is calculated for a Type 2 system, you generally cannot and install a non treated type 1 system. Always ensure you have hired a reputable septic professional and one who can properly assess the land where the system will be installed.

Head over to our Design page to find out more information on the septic system designing process.