Types of Septic Systems
Septic system design and size can vary widely, from within your neighborhood to across the country, due to a combination of factors. These factors include household size, soil type, site slope, lot size, proximity to sensitive water bodies, weather conditions, or even local regulations. Below are ten of the most common types of septic systems used. The list is not all-inclusive; there are many other types of septic systems.
- Septic Tank
- Conventional System
- Chamber System
- Drip Distribution System
- Aerobic Treatment Unit
- Mound Systems
- Recirculating Sand Filter System
- Evapotranspiration System
- Constructed Wetland System
- Cluster / Community System
A buried, watertight tank designated and constructed to receive and partially treat raw domestic sanitary wastewater. Heavy solids settle to the bottom of the tank while greases and lighter solids float to the top. The solids stay in the tank while the wastewater is discharged to the drainfield for further treatment and dispersal.
A decentralized wastewater treatment system consisting of a septic tank and a trench or bed subsurface wastewater infiltration system (drainfield). A conventional septic system is typically installed at a single-family home or small business.
The gravel/stone drainfield is a design that has existed for decades. The name refers to the construction of the drainfield. With this design, effluent is piped from the septic tank to a shallow underground trench of stone or gravel. A geofabric or similar material is then placed on top of the trench so sand, dirt, and other contaminants do not enter the clean stone.
Effluent filters through the stone and is then further treated by microbes once it reaches the soil below the gravel/stone trench.
Gravel/stone systems are relatively large in overall footprint and may not be suitable for all residential sites or conditions.
Gravelless drainfields have been widely used for over 30 years in many states and have become a conventional technology replacing gravel systems. They take many forms, including open-bottom chambers, fabric-wrapped pipe, and synthetic materials such as expanded polystyrene media. The gravelless systems can be manufactured with recycled materials and offer a significant savings in carbon footprint.
An example of a gravelless system is the chamber system. The chamber system serves as an alternative design to the gravel/stone system. The primary advantage of the chamber system is increased ease of delivery and construction. They are also well suited to areas with high groundwater tables, where the volume of influent to the septic system is variable (e.g., at a vacation home or seasonal inn), in an area where gravel is scarce, or in areas where other technologies such as plastic chambers are readily available.
This type of system consists of a series of connected chambers. The area around and above the chambers is filled with soil. Pipes carry wastewater from the septic tank to the chambers. In the chambers, the wastewater comes into contact with the soil. Microbes on or near the soil treat the effluent.