Types of Septic Systems

So you need a septic system. Did you know that means you’re going to have to pick a type of system? There’s a wide variety of system types out there, but before diving into the details of every one, the ten in this post (considered the most common by the EPA) are a great place to start.

The type of system best-suited for you will depend on things like your household size, soil type, lot size, surrounding water bodies, and more. Here’s the very basics on both conventional types of septic systems and common alternative systems.

Septic Tank

The septic tank itself is a buried, watertight holding tank built to hold and do light treatment on a household’s wastewater. Solid matter settles to the bottom of the tank while liquids are discharged to treat and disperse in the soil. Read more about the septic tank here >>

Conventional System

The most conventional kinds of systems have a septic tank and a trench or a drainfield for liquids to disperse into. The practice of using gravel or stone for this drainfield goes back decades — the stone filters out larger contaminants and microbes in the soil below further treats the water. These systems have large footprints and won’t suit all residential sites; though they are most commonly installed in single-family homes or small businesses.  

Chamber System

Gravelless systems have begun to replace traditional gravel systems in recent years. There are many forms of gravelless drainfield, and they offer a smaller carbon footprint than a gravel system does. In a common type of gravelless system, chamber systems, a series of chamber pipes carries the wastewater directly from the tank into the soil. These systems are ideal for areas with higher groundwater tables and where the septic usage volume is more variable. Read more about chamber systems >>

Drip Distribution System

This type of system can be used in many kinds of drainfields. The tank discharge is slowly dripped out in a wide reaching array of shallowly-placed lateral pipes. Drip distribution does require electrical power to regulate the timed drip delivery, and therefore require higher costs and more maintenance. Read more about drip distribution >>

Aerobic Treatment Units

ATUs are like a miniature municipal sewage plant. The treatment tank is injected with oxygen to stimulate natural bacterial activity for further treatment., and some can have additional  tanks to perform more disinfection and pathogen reduction processes. These systems work well in smaller lots, poor soil conditions, and areas with a high water table or nearby surface water. Read more about aerobic treatment >>

Mound System

A mound system will require building an artificial sand mound for the wastewater to be pumped into and flow through before reaching the native soil. This works well in places with shallow soil or bedrock and with high water tables. They do require more space and maintenance than the average. Read more about mound systems >>

Recirculating Sand Filter System

This type of system is more expensive than most conventional systems, but performs a high level of nutrient treatment. After leaving the septic tank, the wastewater will flow into a pump tank which pumps it at a low volume through a sand filter contained with PVC or concrete. Then, like a mound system, the water will filter into the native soil. Read more about recirculating sand filters >>

Evapotranspiration System

In this kind of system, the wastewater will never reach the soil or the groundwater. Instead, it evaporates from the drainfield into the air. This is only workable in arid, hot conditions with shallow soil. Read more about evapotranspiration systems >>

Constructed Wetland System

As the name suggests, this type of system imitates the treatment processes of natural wetlands. After leaving the septic tank, pathogens and other nutrients will be filtered from the wastewater by microbes, plants, and other media, before reaching a drainfield. The plants in these systems need to be able to survive in constantly wet conditions. Only artificial wetlands should be used to treat wastewater; real natural wetlands are not a wastewater disposal or treatment option. Read more about constructed wetland systems >>

Cluster/Community System

Essentially, a cluster or community system is a septic system large enough to handle the wastewater of two or more households or buildings. You’re likely to find them in rural subdivisions, and they will be subject to common ownership. Read more about cluster systems >>

More Information:

• Find diagrams of each type of system at EPA Septic.

• Peruse decentralized wastewater technology fact sheets.

• 5 Factors to Consider When Choosing a Septic Tank from Pete’s Outflow Technicians

• 10 Different Types of Septic Systems + How to Choose the Right One from The Original Plumber. See here for additional info on outdated systems and other FAQs.