How Does a Septic System Work?

Residential Water Treatment Systems | Orenco

How Does a Septic System Work?

Understanding the functionality of a septic system is crucial for homeowners who rely on this method of wastewater treatment. Septic systems are a key component of rural and suburban homes that are not connected to municipal sewer lines. They provide a straightforward and effective way to treat and dispose of household wastewater on-site. This blog aims to demystify the workings of a septic system, exploring its components, processes, and maintenance needs.

So, how does a septic system work?

Introduction to Septic Systems

Septic systems are underground wastewater treatment structures that use a combination of nature and proven technology to treat and dispose of household wastewater. They are typically found in rural areas where municipal sewer systems are not available. Understanding how septic systems work is essential for maintaining them properly and ensuring they function efficiently.

The Components of a Septic System

The Septic Tank

The heart of any septic system is the septic tank. This underground, watertight container is typically made of concrete, fiberglass, or polyethylene. Its primary role is to receive all wastewater from your home, which includes water from toilets, showers, sinks, and washing machines.

Inside the tank, solids settle at the bottom, forming sludge, while oils and grease float to the top as scum. The tank’s design allows for the partial decomposition of solid materials by bacteria, reducing the amount of solid waste that accumulates over time.

The Drainfield

The drain field, also known as the leach field or absorption field, is a subsurface wastewater disposal area. After the wastewater is partially treated in the septic tank, it flows out into the drain field. Here, it percolates through the soil, which provides further treatment by removing harmful bacteria, viruses, and nutrients.

The Process of Wastewater Treatment

Let’s break down the answers to the question: how do septic systems work?

From Household to Septic Tank

The process begins when all the water you use in your home flows into the septic tank through a drainage pipe. The tank’s design allows heavy solids to settle at the bottom, where bacteria break them down. Lighter substances, like oils and grease, float to the top.

Treatment in the Septic Tank

In the tank, bacteria essential to the process digest organic materials in the wastewater. This reduces the solid load by decomposing the material into gases and liquids. However, the tank cannot treat all the material completely, which is why regular maintenance and pumping of the tank are crucial to remove the inorganic and inert solid materials that accumulate over time.

Final Treatment and Disposal

The partially treated water from the septic tank then flows into the drain field, where the final treatment occurs. As the wastewater percolates through the soil, harmful coliform bacteria, viruses, and nutrients are naturally removed. The now-treated water eventually joins groundwater sources, having minimal environmental impact.

Maintenance of a Septic System

Proper maintenance is vital to the smooth operation of a septic system. Regular inspections and pump-outs of the septic tank are necessary to prevent system failure, which can be both costly and unhealthy. Homeowners should be cautious about what goes into their septic system—avoid flushing harsh chemicals, non-biodegradable materials, and excessive amounts of water, as these can disrupt the delicate biological balance required for the system to function effectively.

Common Questions About Septic Systems

How Often Should a Septic Tank Be Pumped?

The frequency of pumping depends on the size of your septic tank and the number of people living in your household. Generally, it’s recommended to pump your septic tank every 3 to 5 years. However, regular inspections can help determine when pumping is necessary.

What Are the Signs of a Failing Septic System?

Signs that your septic system may be failing include unpleasant odors, standing water or soggy soil in your yard, particularly around the drainfield, and slow-draining sinks and toilets. If you notice any of these signs, it’s crucial to contact a septic system professional immediately.

How does a septic system work?

A septic system treats and disposes of household wastewater onsite. It typically consists of two main parts: a septic tank and a drainfield. When wastewater from your home enters the septic tank, it separates into three layers: solids settle at the bottom to form sludge, water occupies the middle layer, and oils and grease float to the top as scum. Bacteria in the tank digest the solids, reducing their volume. The liquid wastewater then flows into the drainfield, where it is further treated by the soil. Harmful bacteria, viruses, and nutrients are removed as the water percolates through the soil layers, eventually recharging the groundwater.

How often should a septic tank be pumped?

The frequency of septic tank pumping varies depending on several factors including the size of your tank, the number of people living in your household, and your water usage habits. Generally, it’s recommended to pump your septic tank every 3 to 5 years. However, regular inspections can help determine more precise pumping schedules. It’s important to monitor your septic system’s performance and consult with professionals to establish a maintenance schedule that suits your specific needs.

What are the signs of a failing septic system?

There are several indicators that your septic system may be failing or in need of maintenance, including:

  • Unpleasant odors around the septic tank or drainfield area.
  • Standing water or persistently soggy soil in your yard, especially near the drainfield, even in dry weather.
  • Slow drains, or backups in sinks, showers, and toilets.
  • Gurgling sounds in the plumbing system.
  • An unusually lush or green lawn over the drainfield, even during dry periods.

If you notice any of these signs, it’s crucial to contact a septic system professional as soon as possible to diagnose and address the issue.

What should not be flushed or poured down the drain in homes with septic systems?

To maintain a healthy and efficient septic system, it’s important to be mindful of what goes down your drains. Avoid flushing or pouring the following items, as they can disrupt the bacterial balance in the tank, clog the system, or contaminate the groundwater:

  • Non-biodegradable items such as plastics, diapers, wipes, and feminine hygiene products.
  • Hazardous chemicals like paint, solvents, pesticides, and high concentrations of cleaning agents.
  • Grease and fats, which can solidify and cause blockages.
  • Medications, which can kill the beneficial bacteria in the tank.
  • Excessive amounts of food waste, coffee grounds, and other solids.

Can I plant anything over my septic system?

While it’s essential to avoid planting trees or large shrubs over your septic system due to the risk of root intrusion and damage, certain types of landscaping can be beneficial. The grass is the best cover for your drainfield, as it helps prevent erosion and assists in the evaporation of excess water. If you wish to add more greenery, opt for shallow-rooted, drought-tolerant plants and flowers. Always ensure there’s easy access to your septic tank for inspections and pumping, and avoid heavy structures or vehicles over any part of the system to prevent damage.


Understanding how septic systems work is essential for anyone who relies on one for wastewater treatment. Proper care and maintenance can prevent costly repairs and ensure that your septic system continues to function effectively for many years. By being mindful of what goes into your system and staying on top of regular maintenance, you can ensure that your septic system remains an efficient and environmentally friendly way to manage household wastewater.

In summary, septic systems play a crucial role in treating and disposing of household wastewater in areas not served by municipal sewer systems. By familiarizing yourself with the components and processes involved in how septic systems work, you can contribute to their longevity and reliability. Regular maintenance, mindful usage, and prompt attention to potential issues can help prevent environmental contamination and ensure that your septic system remains a sustainable solution to wastewater management.