Common Types of Septic Systems

The design, features and size of septic systems vary widely from region to region because of a number of factors. These include soil type, slope of the site, lot area, proximity to other water bodies, household needs, family size, weather conditions and the local regulations.  

Before reviewing the most common types of septic systems , we’ll quickly go through the functioning of a septic tank.

Septic Tank

Your septic tank is buried below the ground, designed and constructed to treat and decontaminate wastewater. Heavy solids settle on the tank’s bottom, whereas lighter materials float towards the top of the surface. The solids remain in the tank and are pumped out at regular intervals. The wastewater is passed onto the drain field, where it is further treated and then disposed into the soil.

Traditional Septic System

A traditional septic system comprises a tank and a drain field and is usually preferred for single family homes or home offices. Made from stone or gravel, the design of the drain field has pretty much remained unchanged over the decades. Wastewater is passed from the tank to a shallow trench, covered by a geofabric or another similar material. This prevents dust, dirt, sand and other contaminants from entering the trench. Wastewater is filtered as it passes through the trench until it reaches the soil beneath, where it is acted upon by microbes.

Generally, drain fields are constructed of a bigger size for effective filtration, and hence, may not be suitable for every site.

Chamber System

For the past 20 years, gravelless drain fields are among the most widely used types of septic systems . These exist in many forms such as an open bottom chamber or a fabric wrapped pipe. Often the components are made up of recycled and synthetic materials like expanded polystyrene, reducing the carbon footprint.

One of the most common types of a gravelless system is the chamber system that can be constructed easily at most locations. Such a system is the preferred choice if groundwater levels are high in the area and if the influent volume is variable, as in the case of a seasonal inn or a vacation home. A chamber unit can also be installed in places where gravel isn’t easily available.

As the name implies, a chamber system comprises several chambers connected to each other in series. Soil covers the area above and below these chambers. Wastewater is carried through pipes into the chambers, where microbes in the soil act on the effluent.

Drip Distribution System

Drip distribution is also one of the most common types of septic systems because they can be used in conjunction with several kinds of drain fields. They are preferable because no large soil mounds are needed; instead, drip laterals are installed such that they are within 6 to 12 inches into the soil from the surface. Drawbacks include setting up a dose tank, along with the septic tank, that would collect wastewater, delivering it into the drip absorption area in a timely manner. Moreover, great power is required, which increases expenses and maintenance frequencies.

Aerobic Treatment Unit

An aerobic treatment unit (ATU) is based on the same principle as a municipal sewage plant, but it is much smaller in size. Oxygen is injected into the treatment compartment through an aerobic system.  S gas is present in greater quantities, natural bacterial activity increases and the effluent is treated more effectively.

Certain aerobic units also feature pretreatment and final treatment tanks for reducing pathogen levels.  These systems can easily be installed in homes that have a smaller lot or in areas where soil conditions are inadequate or the water table is high.

Mound System

Mound systems are installed in sites where the depth of the soil or bedrock is shallow and groundwater levels are high.  A sand mound is constructed to encompass a drain field trench. Effluent enters a pump chamber from the tank, passes through the trench and filters through the soil in prescribed doses.  

Mound systems are recommended for certain soils, but they require significant space for installation and must be maintained periodically.

Recirculating Sand Filter System

A sand filter system can be installed above or below the surface. Effluent is directed from the tank to a pump chamber and then passed through to a sand filter, which is often made from concrete or another suitable material lined with PVC. This filter is actually a box filled with sand. Effluent enters through the pipes from the top at low pressure. As it passes through the pipes, it is treated and filtered through the sand. The treated wastewater then flows into a drain field.

Sand filters are generally installed in areas that lie near water bodies. However, they are one of the most expensive types of septic systems .

Evapotranspiration System

This system features a unique drain field design, the base of which is covered with a watertight material. When wastewater enters the drain field, it is evaporated into the air without being filtered through the soil or reaching groundwater.

An evapotranspiration system is preferred only in dry regions with adequate sunlight and heat. Their functioning is good even if the soil is shallow, but they are prone to damage during rainy and snowy seasons.

Constructed Wetland System

This kind of septic system features the same treatment processes as the ones used in natural wetlands. Wastewater from the tank reaches the wetland; as it passes through the cell, plants, microbes and other substances remove pathogens and decontaminate the fluid. A typical wetland cell is lined with an impermeable substance and is filled with sand, gravel and wetland plants that can live in saturated environments.

If required, the treated wastewater may be discharged into a drain field for further contamination.

Which kind of septic system is installed at your home? Ensure that you get it inspected and pumped regularly for proper functioning. Schedule an appointment with A-Team Plumbing and Drain today.