What Is a Septic Tank and How Does It Work?

The first septic tank as we know it was invented in 1860. Jean-Louis Mouras was determined to create a waste management system that did not involve manually dumping wastewater outside. Inspired by flush toilets from Ancient Greece and Rome, he developed a sealed tank that collected waste as it exited his home. He combined his invention with a cesspool, a container that slowly leaks its contents into the surrounding soil. He used his invention for close to a decade without any issue. His invention eventually caught on in the United States, where other entrepreneurs capitalized on his idea and improved his design. Today, septic tanks are popular solutions to waste management in country homes and are effective at filtering waste as it enters soil. Below you can find information on what a septic tank is, how it works, and the advantages and disadvantages of using a septic system. 

What is a septic tank? 

A septic tank is a buried container that is part of a waste removal system for homes that are not connected to a sewer system. They work in conjunction with a drain field and a series of pipes to remove waste from a home. Many homes in the country that do not have access to a city’s sewer system utilize a septic system to remove wastewater. After initial cost and installation, maintenance expenses for septic systems are very low when they are installed properly. The highest quality and most expensive tanks are made of concrete, but they can also be made of fiberglass and polyethylene. 

How does a septic tank work?

A septic tank is a water-tight container that receives all water drained from a home. When waste collects in a septic tank, it separates into 3 layers: scum, effluent, and sludge.

• Scum is the top layer of waste in a tank. It comprises of oils and fats that float to the top of water when given time to sit. Scum is a byproduct of cooking grease, soap, and other fats that may stem from cleaning products or washing hands.
• Effluent is the middle layer of waste that is composed of water leftover after scum has floated to the top and sludge has sunk to the bottom of the tank. Effluent is pumped through the tank outlet into the drain field, where it is dispersed into soil.
• Sludge is the bottom layer of waste in a septic tank. It is comprised of solid waste that sinks to the bottom of the tank as it separates from water. Sludge also consists of byproducts of other waste that decomposes in the tank.

A septic tank relies on bacteria to break down solid waste that settles to the bottom. Once the solids are broken down to a liquid, they are pumped out into the drain field. The drain field works in conjunction with the septic tank. Waste that contains enough liquid to be pumped out of the tank is emptied into soil through the drain field.

Problems may arise if the sludge layer of a tank becomes too high. This can clog the outlet pipe and prevent water from exiting to the drain field. When this happens, puddles will form in your yard as the tank overflows. When you get your tank emptied, a bacterial additive can be added to increase the efficiency of bacteria breaking down sludge into liquid.

Septic tanks are typically made of concrete, fiberglass, or polyethylene. These materials are ideal because they are not prone to cracking while underground. If a septic tank cracks, waste will leak out and form a puddle on the surface above the tank. A septic tank holds wastewater for long enough for solids and oils to separate.

What are the parts of a septic system?

A septic system collects all wastewater from a home, breaks it down, and disposes it. The following parts work together to help a septic system function:

• Drain line
• Septic tank
• Drain field
• Drain box
• Soil

Drain line

All plumbing in a home with a septic system converges at the drain line. The drain line then feeds all wastewater from a home into the septic tank.

Septic tank

The septic tank receives wastewater from the drain line. Once inside the tank, liquid waste pumps into the drain field. Solid waste settles to the bottom of the tank in the form of sludge. Natural bacteria eventually break down the sludge so it can be pumped into the drain field.

Drain field

The drain field, also known as a leach field, receives liquid waste from the tank’s outlet and disperses it into the soil. Drain fields comprise of downward-sloped underground pipes and gravel to spread wastewater from the septic tank. The arrangement of a drain field’s components is designed to avoid wastewater reaching the surface of your yard and to prevent runoff.

Distribution box

The distribution box is a concrete or plastic cube designed to distribute wastewater evenly among a drain field or series of drain fields. It contains multiple outlets to various sections of a drain field, ensuring that each region of the field receives equal amounts of water. The distribution box sits lower than the septic tank and utilizes gravity both to receive wastewater from the tank and to distribute it to the drain field.

Soil

Soil is a critical piece of a septic system as it is the final treatment for wastewater. Once water enters the drain field and percolates down, soil eliminates bacteria, viruses, and nutrients in the waste. Not all types of soil are effective at treating septic waste. Loamy soils, soils with a variety of particle sizes, are the best for septic systems because they do not clog easily. Soils that absorb water easily, such as clay and silt, absorb water and are prone to clogs.

Advantages of septic systems

There are many positives in owning a home with a septic system.

• Septic systems are more environmentally friendly than a sewer system when properly maintained.
• Septic tanks can last for decades. The lifespan of a septic system ranges from 15 to 40 years depending on how well it is installed and maintained.
• Unless your tank runs into problems, they are more cost efficient than using a sewer system. You will need to spend anywhere from $200 to $600 every few years to get your tank emptied. Outside of the initial setup cost, septic systems are relatively cheap compared to using a city sewer system.

Disadvantages of septic systems

Mặc dù bể tự hoại là hệ thống loại bỏ chất thải tuyệt vời, một số vấn đề có thể phát sinh khiến chúng hoạt động không chính xác. Sau đây là những nguyên nhân phổ biến gây ra sự cố trong bể tự hoại:

While septic tanks are excellent waste removal systems, some problems may arise that can cause them to operate incorrectly. The following are common causes of problems in septic tanks:

• They require maintenance. Not keeping up with your tank’s maintenance can cause it to clog or crack. If the sludge layer at the bottom of a tank becomes too high, it can clog the outlet and backup the drains in your home. Septic tanks typically require emptying once every 3 to 5 years. Some tanks may need to be emptied more or less frequently depending on how many people live in a home. You can tell if your septic tank is too full if drains are backed up or slower than normal, water puddles above the septic tank, or if you detect foul odors coming from the tank. You can learn more about how to maintain your septic system on our blog.
• They can be compromised by tree roots. Roots can infiltrate septic pipes if they grow in the vicinity of a tank. If your driveway becomes cracked, you notice puddles in your yard, or your drains become backed up, tree roots may have pierced your pipes. New plastic septic pipes can withstand pressure from tree roots and will prevent them from becoming an issue. If you plan on planting new trees, ensure you keep an appropriate amount of distance between them and your septic system.
• They can overflow. Choosing too small of a size for your tank can cause it to overflow if water usage exceeds its capacity. Generally, you should use a tank 400 gallons larger than the amount of water your household uses in a day. If you use 300 gallons of water per day, you should invest in at least a 700-gallon tank. If you install too small of a tank, it will overflow and cause puddles in your yard. If you regularly host guests or large parties, you will want to purchase a much larger tank than your everyday household usage.
• They can break due to ground movement. Ground movement can force pressure onto the tank and cause structural damage. A small shift in the area surrounding your tank can crack its exterior. If your tank cracks, it will leak wastewater and cause puddles in your lawn.

Learn more: How To Improve Water Quality Parameters With Chemical-Free Nanobubbles 

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Translator: Duong Nguyen Hoang Khang