How Does A Septic Tank Work?

Managing wastewater effectively is essential for hygiene, safety and quality of life. With these factors in mind, septic systems provide a useful solution – historically, they have been used in rural areas that are not connected to municipal sewer systems. In industrial and commercial settings, installing a robust septic system solution can save thousands of dollars over the lifetime of the system.

If you’re new to the concept of septic systems, you may be wondering how they work and the functions they perform. In this article, we’ll walk you through the various types of septic systems, and help you understand them in more detail.

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What Are The Three Types Of Septic Systems?

A septic system transports sewage and waste products away from your building, ensuring that wastewater is disposed of properly and safely. Residential and commercial systems operate in similar ways, but commercial septic systems are usually bigger and have high-capacity tanks. 

Septic tanks are usually constructed out of concrete, fiberglass or polythene. Concrete is most often used as it provides a durable, long-lasting and affordable solution.

There are three main types of septic systems that are commonly used:

  • Conventional Septic Systems
  • Pressure Distribution Septic Systems
  • Aerobic Treatment Units (ATUs)

Conventional Septic Systems

As the name suggests, conventional septic systems are the most commonly used of these three solutions. They are also known as gravity septic systems. A conventional system carries wastewater from toilets and drains to a septic tank, which separates solids and liquids. Solids are kept in the septic tank, while liquids are drained into a drain field where it is treated by the surrounding soil. A conventional septic system is ideal for properties with good drainage conditions.

Pressure Distribution Septic Systems

Pressure distribution systems operate in a similar manner to conventional systems, but are best utilized when soil conditions are poor for distributing waste products. These systems include a high-pressure pump that is able to force effluent into a wider area across the drain field.

Aerobic Treatment Units (ATUs)

Aerobic Treatment Units (ATUs) are used when soil conditions and other factors can make conventional systems unsuitable. ATUs use oxygen to break down waste products, compared with conventional septic systems that use an anaerobic process. This type of septic system can be extremely effective, but aerobic systems are typically more expensive than anaerobic ones. 

How a Septic Tank Works

The concept of a septic system is relatively simple. Importantly, maintenance of the septic tank and the surrounding parts can help to ensure that the system works effectively. For industrial and commercial users, due diligence in advance of purchase – and working with a trusted provider – can provide peace of mind for decades to come.

Below is the process for how a septic system operates:

  1. Wastewater from toilets and drains is flushed through an exit pipe into the septic tank.
  2. Solids and liquids are separated; solids sink to the bottom. 
  3. Bacteria introduced into the septic tank helps to break down the solid waste. Filters help to prevent the solid waste from leaking out into the drainfield.
  4. Liquid (also known as effluent) is partially treated by bacteria in the septic tank, before being emptied into the drainfield.
  5. The effluent drains through the soil layers, where it is filtered. The effluent is fully treated by the time it discharges to groundwater.


Parts of a Septic Tank System

The key components of a septic tank system are as follows:

  • Septic Tank – This is the buried, watertight container where wastewater is collected. It can be made from concrete, plastic or fiberglass. As described above, the tank works by separating solids from liquids. Lighter materials (such as oil and grease) float to the top and form a layer of scum.
  • Drain Field – Drain fields are a series of perforated pipes that are buried in trenches under the ground. Effluent from the septic tank flows into these pipes and is then dispersed into the soil.
  • Distribution Box – The distribution box ensures that effluent is evenly distributed across the drain field.
  • Vent Pipes – The vent pipes ensure that gasses produced in the septic tank can escape into the atmosphere, thus preventing pressure building up.
  • Soil – The soil underneath the drain field is the final treatment and disposal area for the wastewater. It filters out impurities before the wastewater returns to the groundwater.
  • Baffles – Baffles help to prevent the scum layer from exiting the tank, and the sludge layer from entering the outlet.
  • Access Risers & Manholes – These are used for inspections and maintenance, ensuring access to the system if necessary.


Even if they are rarely seen, an effective septic system is an essential part of the everyday operations of many industrial and commercial operations. At Jensen Precast, we offer a wide variety of septic tank solutions in a number of sizes. Our team’s experience and expertise can help guide you to find an environmentally friendly and cost-effective solution. 

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