What Are Septic Tanks? Your Comprehensive Guide

It’s a question we are often asked, what are septic tanks? Septic tanks are underground structures that are used to treat and dispose of household wastewater from commercial and domestic properties in rural areas where there is no access to a public sewer system.

Their purpose is to separate solid waste from liquid waste, allowing the liquid to flow out of the tank and into the surrounding soil, where it is further treated by natural processes.

Homeowners and property owners are responsible for maintaining the efficiency of septic tanks by not disposing of non-biodegradable items, chemicals, or excessive amounts of water down their drains.

Regular inspections and pumping of the tank are also necessary to prevent blockages and overflows.

Typically located in the garden or yard of a domestic dwelling, septic tanks are connected to the household plumbing system, receiving wastewater from toilets, sinks, showers, and laundry facilities.

Once inside the tank, the wastewater undergoes a process of natural decomposition as solids settle at the bottom and scum floats to the top, while the liquid effluent is discharged through a series of pipes into the surrounding soil for further treatment.

This article goes into greater depth outlining the differences in these types and tanks. Read on to learn everything you need to know about what are septic tanks.

How Does a Septic Tank Work?

how does a septic tank work

Septic tanks are situated underground in both residential and commercial properties, although this post will concentrate on residential homes rather than business establishments. They are designed to store and partially treat sewage and wastewater from commercial or domestic sources.

Here’s a summary of how septic tanks work:

  • Wastewater Collection: Homes or buildings send wastewater from toilets, sinks, and showers into the septic tank.
  • Separation of Solids and Liquids: Once in the tank, the waste separates into three layers:
    • Top Layer of Waste (Scum): Consists of oils, grease, and other light substances.
    • Middle Layer of Waste (Liquid Effluent): Mainly greywater which can flow out of the tank.
    • Bottom Layer of Waste (Sludge): Heavier solids that settle at the bottom.
  • Decomposition of Solids: Bacteria in the tank naturally break down the organic material in the sludge and scum, reducing their volume.
  • Effluent Disposal: The liquid effluent in the middle layer flows out of the tank into a drainage field or leach field. Excess water is eliminated into the soil or seeps into a layer of gravel.
  • Soil Filtration: As effluent percolates through the soil in the leach field, it is further treated through natural processes. The soil acts as a biological filter, removing harmful bacteria, viruses, and nutrients.
  • Maintenance and Pumping: Over time, the sludge accumulates and needs to be pumped out to prevent the system from clogging and malfunctioning. Any discharge must not be dispersed to surface water areas including streams, rivers and ditches as well as canals.
  • Environmental Protection: Properly functioning septic systems treat wastewater effectively, protecting groundwater and surrounding ecosystems from contamination and lowering organic matter.
The Importance of Septic Tank Groundwork

The term ‘septic’ indicates the presence of microorganisms, and septic systems are a way for homeowners to dispose of household plumbing when there is no connection to the mains sewer.

The septic tank consists of a large, watertight container typically made of concrete, fibreglass, or plastic. It is buried underground and connected to the plumbing system of the house through an inlet pipe.

All wastewater from toilets, sinks, showers, and other plumbing fixtures in the house flows into the septic tank through this inlet pipe.

Septic tanks are designed to hold and treat the wastewater produced by a household. They work by allowing the wastewater to separate into three layers inside the tank. The solid waste settles at the bottom of the tank and forms a layer called sludge.

Grease and oils float to the top and create a layer called scum. The remaining liquid, known as effluent, is located in the middle layer.

Septic tanks are typically made of concrete or fibreglass and are buried underground near the homes they serve. They have an inlet pipe that connects to the household plumbing system, allowing wastewater from toilets, sinks, showers, and laundry machines to enter the tank.

The lifespan of a septic tank can vary based on factors such as ground conditions and maintenance.

What Are Septic Tanks Functions?

Septic tanks play a crucial role in the treatment of wastewater from households and commercial buildings. They are designed to separate solids and liquids in the waste water through decantation and sedimentation. In this process, the heavier solids settle to the bottom of the tank, while

Single-Chamber vs. Multi-Chamber Tanks

Single-chamber tanks consist of a single compartment for processing sewage and wastewater, while multi-chamber tanks have multiple compartments that allow for further treatment and separation of solids and liquids.

Single-chamber tanks typically only have one outlet for discharging treated effluent, while multi-chamber tanks may have multiple outlets for more controlled discharge, with the middle layer known as effluent only being allowed to flow out into the septic field.

In terms of installation, single-chamber tanks are generally simpler and require less space, making them suitable for smaller properties with limited space.

Septic Tanks vs Wastewater Treatment Systems

They are often made of concrete or plastic and can be installed at a shallower depth. Multi-chamber tanks, on the other hand, are larger and more complex, requiring a larger installation area and are often made of concrete.

Legislation and site requirements also play a significant role in determining the type of tank needed.

Some jurisdictions may have specific regulations regarding the use of single-chamber or multi-chamber tanks, and site conditions such as soil type and water table levels can also influence the choice of tank.

Overall, the choice between single-chamber and multi-chamber tanks depends on factors such as the size and shape of the property, processing and discharging requirements, and compliance with legislation and site conditions.

Operation and Septic Tank Maintenance

Septic tanks are essential to proper functioning of a home’s wastewater management system.

From regular maintenance to the occasional need for repairs, knowing how to take care of your septic tank is crucial for avoiding costly and messy issues down the line.

Understanding the ins and outs of septic tank care will help ensure the longevity and efficiency of any home’s wastewater system.

Regular Maintenance Requirements

Regular maintenance of a septic system is vital to ensure its proper functioning and longevity.

This includes:

  • Inspecting the tank for any damage or leaks,
  • removing settled solids annually to prevent buildup,
  • and ensuring proper drainage field maintenance to avoid any clogs or blockages.

It is also important to arrange for upstream maintenance regularly to prevent any issues with the system, such as making sure that no harmful chemicals or large amounts of water are being flushed into the system.

By staying on top of regular maintenance, you can prevent costly and potentially hazardous problems with your septic system. It’s important to schedule regular inspections and cleanings to keep your septic system running smoothly and efficiently.

The Importance of Pumping Out the Tank Periodically

Pumping out the septic tank periodically is crucial for several reasons.

  • First and foremost, regular pumping helps prevent the build-up of sludge, which can clog the system and lead to potential health hazards.
  • Secondly, maintaining a healthy level of bacteria in the tank is essential for its proper functioning, and regular pumping can help with this.

It is recommended on a regular basis to empty the tank every 1-3 years, depending on usage levels, to ensure it remains in good condition. Larger tanks require emptying every 3-5 years.

Neglecting this maintenance can lead to the tank becoming too full, which may result in overflow or blockages. To ensure the task is done effectively, it is important to use a specialist company for septic tank pumping.

By taking the necessary steps to pump out the septic tank regularly, homeowners can prevent sludge build-up, maintain the tank’s performance, and avoid potential health hazards.

How Septic Tanks Work

This simple maintenance task goes a long way in ensuring the proper functioning of the septic system and preventing costly repairs down the line.

Septic Tank Effluent and Wastewater Treatment

Septic tank effluent and wastewater treatment involve the process of removing solids and impurities from the wastewater before it is discharged into the environment.

Decantation and sedimentation are key processes used to eliminate solids from the wastewater.

During decantation, the wastewater is allowed to settle, allowing heavier particles to sink to the bottom. Sedimentation involves the separation of solids from the liquid through gravity, further reducing the amount of suspended solids in the wastewater.

Septic tanks can be constructed using various materials such as concrete, fibreglass, plastic, and steel. Each material has its own set of advantages and disadvantages, including durability, cost, and ease of installation.  Concrete tanks are substantially heavier with fibreglass and plaster being much lighter.

How Septic Tanks Handle Domestic Wastewater

Septic tanks handle domestic wastewater by collecting the wastewater from the house’s plumbing system and retaining it for some time to allow for the separation of solids, such as sludge and scum, from the liquids.

The solids settle at the bottom of the tank, while the lighter scum floats to the top.

The liquid wastewater, or effluent, is then discharged from the tank into the surrounding soil through a series of pipes to be further treated by the soil.

The purpose of septic tanks in treating wastewater from rural homes is to provide an efficient and reliable way to manage domestic wastewater in areas where centralized sewer systems are not available.

Homeowners are responsible for ensuring the efficiency of their septic tanks through regular maintenance, such as routine inspections, pumping out the solids, and avoiding the disposal of harmful substances down the drains.

The Role in the Treatment and Disposal of Sewage

Sewage treatment plants and septic tanks both play a crucial role in the treatment and disposal of sewage.

Sewage treatment plants are large facilities that receive sewage from a network of underground pipes and treat it to remove contaminants before discharging the treated effluent into a water body.

On the other hand, septic tanks are smaller, onsite sewage treatment systems commonly used in rural areas.

They treat sewage using naturally occurring bacteria and then discharge the effluent into a drain field, where it percolates into the soil.

The effluent treatment capabilities of sewage treatment plants are typically more advanced and can remove a wider range of contaminants compared to septic tanks.

Additionally, sewage treatment plants can handle a larger volume of sewage and are equipped with processes for further treatment such as disinfection.

Which Septic Tank is Best for Your Home or Business?

In the UK, there are general binding rules for septic tanks and small sewage treatment plants, which outline the requirements for their installation and maintenance to protect the environment and human health.

Compliance with these rules is crucial to prevent pollution and minimize the environmental impact of sewage disposal.

Key factors contributing to sewage treatment plants’ effectiveness in reducing environmental impact include advanced treatment processes, proper maintenance, and regular monitoring to ensure compliance with regulatory standards.

By effectively treating and disposing of sewage, both sewage treatment plants and septic tanks play a vital role in protecting public health and the environment.

Components of a Septic Tank System

As you know, septic tank systems are an essential component of a home’s wastewater management, especially in areas where municipal sewer systems are not available.

These systems are responsible for treating and disposing of household sewage safely and efficiently.

Understanding the components of a septic tank system is crucial for maintaining its functionality and preventing issues such as backups and contamination.

From the tank itself to the drain field and everything in between, each component plays a vital role in ensuring the proper treatment and disposal of wastewater.

Let’s explore the various components of a septic tank system and their importance in the overall function of the system.

The Inlet Pipe

The inlet pipe is a crucial component of the septic system, responsible for allowing raw wastewater to enter the septic tank for treatment. Typically made of PVC or ABS plastic, the inlet pipe is designed to withstand the corrosive nature of wastewater.

The inlet pipe connects the plumbing system in your home to the main sewer line that leads to the septic tank. Once raw wastewater exits the plumbing system, it travels through the main sewer line, eventually entering the septic tank through the inlet pipe.

This allows the wastewater to begin the treatment process within the septic tank before it eventually moves on to further treatment and disposal.

The inlet pipe serves as the entry point for raw wastewater into the septic tank, connecting the plumbing in your home to the main sewer line that leads to the tank. Its durable construction and strategic placement are essential for the proper functioning of the septic system.

The Outlet Pipe

The outlet pipe is an essential component of the overall system. It serves as the means through which treated wastewater flows out of the tank and into the drainfield or leach field for further purification and dispersal.

To check the condition and flow of the septic tank outlet pipe, start by visually inspecting the pipe for any signs of damage, clogs, or leaks.

Next run, water through the system to see if it flows smoothly and quickly through the outlet pipe.

Septic Tank Installation Contractors and Why You Need One

If there are any issues with the flow, it may indicate a blockage or damage in the pipe that needs to be addressed.

In cases where the septic tank outlet pipe needs to navigate uneven terrain, such as slopes or embankments, gravity flow may be hindered, leading to potential issues such as slow drainage or backups.

In such situations, a pump station may be necessary to assist with the movement of wastewater from the septic tank to the drainage field.

A pump station can help by lifting the wastewater to a higher elevation or pumping it through a longer distance, compensating for the challenges of uneven terrain.

Regular inspection and maintenance of the septic tank outlet pipe, along with considering the need for a pump station in cases of uneven terrain, can help prevent potential issues and ensure the proper functioning of the septic system.

Dip Pipe

The dip pipe plays a vital role in ensuring the proper functioning and efficiency of the system. Its primary function is to provide a direct path for the substance to be removed from the bottom of the tank without disturbing the contents.

This is essential for maintaining the quality and integrity of the stored material.

The dip pipe is typically designed with a curved or angled end to prevent the intake of any sediments or solids present in the tank, ensuring that only the desired substance is withdrawn. This helps to maintain the purity of the withdrawn material and prevents any potential contamination.

Drainage Pipe

A drainage pipe is an essential component of a septic tank system. It is responsible for carrying the effluent or wastewater from the septic tank to the drain field, where it gets dispersed into the soil through a network of pipes.

This helps to fill the drainage pipe more evenly and extend the drainage field life by preventing premature clogging or bio-clogging.


Septic tanks are underground chambers used for the treatment and disposal of wastewater in areas where there is no access to a centralized sewage system. They are commonly found in rural and suburban areas, as well as in some older urban homes.

  • Septic tanks are underground structures used to treat and dispose of household wastewater in areas without access to a public sewer system.
  • They separate solid waste from liquid waste, allowing the liquid to flow into the surrounding soil for further treatment.
  • Regular maintenance and pumping of the tank are necessary to prevent blockages and ensure its efficiency.

Hopefully, this article has helped you understand what are septic tanks, but if you need more information or have general questions about what tank or wastewater treatment system is right for you, then please don’t hesitate to get in touch.

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Updated: January 13, 2024

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Septic TanksWhat Are Septic Tanks? Your Comprehensive Guide