What is a Septic Tank and How Does It Work?

 

Septic tanks are essential for managing waste in areas without a central sewer system.

They provide a safe, efficient way to handle household wastewater.

But what exactly is a septic tank and how does a septic tank work?

In this article, we’ll explore what septic tanks are, how they work, and why they’re important.

We’ll also look at their benefits, downsides, and alternatives.

What is a Septic Tank?

A septic tank is an underground system used to treat household wastewater in areas without a central sewer connection.

It collects and holds wastewater from sinks, toilets, showers, and drains.

The tank separates waste into three layers: solids (sludge) settle at the bottom, liquids (effluent) stay in the middle, and oils or fats (scum) float to the top.

Septic tanks are commonly used in rural or remote areas where connecting to a central sewage system is impractical.

They provide an effective and self-contained way to manage household wastewater.

How Does a Septic Tank Work?

A septic tank operates through natural processes of separation and filtration.

Here’s a closer look at how a septic tank works.

Wastewater Enters the Tank

All wastewater from the home flows into the septic tank through pipes.

This includes water from toilets, sinks, showers, and laundry machines.

As the wastewater enters the tank, gravity causes it to separate into different layers.

Separation of Waste

Once inside the septic tank, the waste separates into three layers:

Sludge (solids)

Heavy solids settle at the bottom of the tank. These solids accumulate over time and need to be pumped out periodically.

Effluent (liquid)

The middle layer consists of liquid waste, or effluent. This layer contains water, dissolved materials, and some small particles.

Scum (fats and oils)

The top layer is made up of lighter materials like fats, oils, and grease. These float on top of the liquid.

Bacterial Breakdown

Inside the tank, naturally occurring bacteria break down some of the solid waste.

This process reduces the amount of sludge at the bottom.

However, the bacteria cannot break down everything, so the tank must be pumped out regularly to prevent overflow.

Effluent Moves to the Drain Field

Once the waste has separated, the effluent, or liquid waste, exits the tank through an outlet pipe.

It then flows into a drain field, also called a leach field.

The drain field is a network of perforated pipes buried in the ground.

These pipes distribute the effluent into the surrounding soil.

Natural Filtration in the Drain Field

In the drain field, the effluent slowly seeps into the soil.

The soil naturally filters out harmful bacteria, nutrients, and contaminants, making the water safe before it re-enters the groundwater system.

The size and design of the drain field are important to ensure the effluent is properly filtered.

Waste Accumulation

Over time, sludge and scum accumulate in the septic tank, and one common question is – how often should septic tanks be emptied? 

To prevent the system from backing up or overflowing, homeowners need to pump out the tank every three to five years.

Regular maintenance ensures the system functions efficiently and prevents costly repairs.

Why are Septic Tanks Used?

Septic tanks play an important role in managing household wastewater, especially in areas without access to a central sewer system.

They are essential for homes in rural or remote locations where a municipal sewage system is either unavailable or impractical.

Waste Management in Rural Areas

In rural areas, connecting to a central sewage system can be too costly or impossible due to the distance from urban infrastructure.

Septic tanks provide an efficient, independent solution for treating wastewater on-site, making them the go-to option for homes, farms, and cottages.

Affordable and Practical Solution

Installing a septic tank is often cheaper than connecting to a sewer system in areas where sewage lines are not present.

Once installed, septic systems are low-maintenance, with only occasional pumping required.

This makes them an affordable long-term solution for households.

Environmental Benefits

Septic tanks use natural processes to treat wastewater.

After separating solids, the liquid is filtered through the soil in the drain field, reducing the environmental impact compared to centralised sewage treatment plants.

For those in rural settings, septic tanks offer a sustainable and practical approach to managing household waste while protecting the environment.

What are Septic Tanks Made of?

Septic tanks are typically made of three main materials: concrete, plastic, and fibreglass.

Concrete

Concrete septic tanks are strong and durable, often lasting several decades. They are heavy and resistant to cracking but can be difficult to install.

Plastic

Plastic tanks are lightweight, easier to install, and resistant to rust and corrosion, but they can be more prone to damage during installation.

Fibreglass

Fibreglass tanks are also lightweight and highly resistant to cracking or corrosion. They tend to be more expensive but are durable and easier to handle than concrete.

What are the Benefits to a Septic Tanks?

Septic tanks offer several advantages, particularly for homeowners in rural or remote areas where central sewer systems aren’t available.

Cost-Effective Solution

Septic tanks provide an affordable alternative to connecting to a sewer system, especially in areas where such connections would be expensive.

The initial cost of installation can be lower, and ongoing maintenance costs are typically minimal, requiring only periodic pumping every few years.

Environmentally Friendly

Septic systems use natural processes to treat wastewater.

After separating solid waste, the liquid is filtered through the soil in the drain field, where harmful bacteria and contaminants are removed naturally.

This eco-friendly method reduces environmental impact compared to large sewage treatment plants.

Self-Sufficient and Reliable

Homes with septic systems are independent of municipal sewage lines, making them more self-sufficient.

Septic tanks are particularly useful in rural or off-grid locations, providing reliable wastewater treatment without depending on public infrastructure.

Long Lifespan with Proper Maintenance

With regular maintenance, such as pumping out accumulated sludge every three to five years, septic tanks can last several decades.

They are durable and effective for long-term waste management.

Minimal Operating Costs

Once installed, septic systems have minimal day-to-day operating costs.

Regular inspections and pumping are the only major expenses, making them a low-cost solution over time.

What are the Downsides to a Septic Tank?

While septic tanks offer numerous benefits, they also come with some drawbacks that homeowners should consider.

Regular Maintenance Required

Septic tanks require ongoing maintenance to function properly.

Over time, solid waste accumulates at the bottom of the tank, and if not removed, it can lead to clogs, overflows, or backups, requiring the septic tank to be cleaned.

The tank needs to be pumped out every three to five years, depending on usage.

Neglecting this maintenance can result in expensive repairs or environmental contamination.

Limited Capacity

Septic tanks have a finite capacity for handling waste. In large households or homes that generate a significant amount of wastewater, the tank may fill up more quickly.

Overuse can cause system failures, requiring more frequent pumping or even the installation of a larger tank.

Potential for Environmental Damage

If not properly maintained, a septic system can leak, allowing untreated wastewater to contaminate nearby soil, groundwater, or surface water.

This poses a risk to the environment and can affect local water sources, including wells and streams.

Not Suitable for Every Location

Septic tanks rely on the soil to naturally filter and treat effluent.

In areas with poor drainage, rocky soil, or a high water table, a septic system may not work efficiently.

In these cases, alternative solutions like mound systems may be required, which can be more expensive to install.

Initial Installation Cost

While septic tanks are cost-effective over time, the initial installation can be expensive, especially if specialised equipment or excavation is needed.

What are the Alternatives to a Septic Tank?

While septic tanks are widely used in rural or off-grid areas, there are several alternatives available for treating household wastewater.

These options can be more suitable in specific conditions or preferences.

Sewer System

The most common alternative is connecting to a municipal sewer system, where available.

This option provides reliable wastewater treatment through a centralised facility.

It eliminates the need for on-site systems and reduces maintenance, though connection fees and monthly bills apply.

Aerobic Treatment Systems

Aerobic systems function similarly to septic tanks but introduce oxygen into the wastewater treatment process.

This helps bacteria break down waste more efficiently and quickly.

These systems are ideal for areas with poor soil drainage but require more maintenance and can be costlier to install than septic tanks.

Composting Toilets

Composting toilets are waterless systems that decompose human waste through aerobic processes.

These systems are ideal for remote locations with limited water supply or environmental concerns.

Composting toilets require minimal infrastructure but need regular care to manage the composting process.

Mound Systems

Mound systems are used when the soil isn’t suitable for a traditional septic drain field.

A mound of sand or gravel is created above ground, allowing effluent to be filtered through the artificial mound.

While effective, they are more expensive to install.

Constructed Wetlands

This eco-friendly option mimics natural wetlands to treat wastewater.

It involves a series of shallow ponds planted with vegetation that filter and break down waste.

Though land-intensive, constructed wetlands offer a sustainable alternative for treating wastewater.

Conclusion

You should now have the answers to the question of ‘how does a septic tank work?’.

Septic tanks are an essential part of wastewater management in areas without a central sewer system.

They work by separating solid waste from liquid, allowing bacteria to break down the solids. The liquid is then filtered by the soil in the drainage field.

Septic tanks are cost-effective, long-lasting, and environmentally friendly, but they require regular maintenance to function properly.

While they offer many benefits, they also have downsides, including the potential for leaks and the need for regular maintenance.

If a septic tank isn’t the right solution, alternatives such as aerobic treatment systems or composting toilets may be a better fit.

In any case, choosing the right wastewater system depends on your location, budget, and needs.

For more help or advice on septic tanks, or other drainage needs, get in contact with us here at KD Drainage.