How Does a Septic Tank Work?

A septic tank is a buried container that holds wastewater long enough to separate solids from liquids. Heavy solids settle to the bottom forming sludge, while oils and grease float to the top forming scum.

Liquid waste leaves the tank through perforated pipes into an absorption field (sometimes called a drain field or leach field). Gravel and soil act as biological filters to purify the water. Click the to know more.

All of the wastewater that leaves your house from your toilets, sinks, garbage disposal and washing machine flows to your septic tank. The tank is an underground container usually made of concrete, fiberglass or high-density polyethylene. The wastewater enters the septic tank where anaerobic bacteria begin breaking down organic matter. The solid waste then settles to the bottom of the tank as sludge and the oil and other liquids float to the top as scum. A septic tank can be sized to meet the needs of your household.

The wastewater is then dispersed into the septic system’s drain field through pipes. The soil in the drain field biologically treats the wastewater. Ideally, the soil in the drain field gets rid of all bacteria and viruses in the wastewater. However, if the soil in the drain field is too compacted or filled with rocks or gravel, it can’t effectively treat wastewater.

If the septic system is not working properly, wastewater can overflow into the drain field or enter nearby drinking water wells and waterways. These untreated pollutants can cause health problems for people and animals. Excess nutrients like nitrogen and phosphorus can also cause cyanobacteria, or harmful algal blooms, that deplete oxygen in waterbodies and can kill fish and other wildlife.

To prevent this, a septic tank should be regularly inspected and maintained. A septic system can be inspected by a professional who can measure the layers in the tank, determine how much sludge is present and pump the septic tank when necessary. A septic tank should be pumped every two to three years. It is a good idea to keep records of the septic tank’s pumping, inspection and maintenance.

It is also important to maintain the septic system by keeping the drain field free of vegetation that can grow into the pipes. In addition, it is a good idea to add 8 to 12-inches of mulch over the absorption field to protect the soil. It is also a good idea to install low-water using appliances and fixtures in your home to reduce your household wastewater.

How does a septic tank work?

Whether you have an older home with a septic system or a newer one, understanding how it works helps you to avoid common problems that can cause wastewater to back up into your house. The septic tank is a big, concealed rectangular or cylindrical vessel made of concrete, fiberglass or polyethylene that sits underground. It has a main drainage pipe, also known as an inlet pipe, on one side and an outlet pipe on the other. In between is a network of perforated pipes that extend into the drainfield’s soil.

All water waste from your house goes into the septic tank through the inlet pipe. When the septic tank fills, solid waste settles in three layers: the heavy sludge layer sinks to the bottom of the tank; the middle layer contains water along with lighter particles that float; and the top layer is comprised of oils and grease. Bacteria in the septic tank slowly decompose these particles, which separates the liquid from the sludge. The liquid, which is referred to as effluent, exits the tank through the outlet pipe. This wastewater trickles through the drain field, where bacteria further treat it before it enters groundwater.

Septic systems are reliable and rarely fail if properly maintained. However, homeowners should be careful about what they put down the drains. For example, it is important to never flush paper towels, diapers, sanitary products, cigarette butts, pet feces, pharmaceuticals or paint thinner down the drain. These items can kill the bacteria that are responsible for breaking down the solid waste in your septic tank.

It’s recommended that homeowners install a two-compartment tank, which treats the wastewater in two stages before it leaves the tank. This reduces the amount of pressure on one septic tank and prevents it from overflowing. In addition to this, homeowners should have the septic tank pumped regularly to ensure that it stays empty. If the septic tank becomes overfull, it can clog the inlet and overflow into the home. You can determine when your septic tank is full by observing the sludge and scum levels or by using an electronic monitor that alerts you when the effluent level has reached its preset limit.

What are the benefits of a septic tank?

Septic tank systems are a reliable and cost-effective way to manage household waste. If homeowners keep the system maintained and are careful with water usage, a septic tank can last for decades without any major problems. However, like anything that is used frequently, a septic tank can develop issues over time. These issues include a clogged drain line, a full septic tank and leaky pipes. When these issues occur, they can result in sewage backing up into the home or groundwater supplies.

A septic tank is a large concrete or plastic container that holds the wastewater produced in your home. It’s buried underground and has a lid that is kept closed with a latch. When you use your toilets, washrooms and kitchen, wastewater flows into the septic tank. There, it separates into three layers: solids at the bottom, scum on top and liquid effluent in the middle. Bacteria in the septic tank break down these materials for safe disposal.

When the wastewater reaches the end of its life in your septic tank, it flows into a drain field. The drain field is also known as an absorption field, a leach field or a gravel-lined septic system. This area is surrounded by soil and has holes in the gravel that allow the wastewater to seep into the dirt. The soil and grass above the holes filter out the harmful bacteria in the water.

The drain field must be well-maintained to prevent clogs and overflowing. You can help prevent clogs by adding 8 to 12 inches of mulch around the septic tank, pipes and drain field. The mulch helps keep the soil from compacting and will help reduce the amount of organic debris that enters the drain field.

Another way to avoid clogs and overflowing is to install a garbage disposal that uses an anaerobic process. This type of garbage disposal breaks down the food waste and other material faster than standard garbage disposals, which can cause a lot of sludge to build up in the septic tank and the drain field.

A septic system needs to be regularly inspected. The inspector will check for clogs, leaking pipes and other problems. The inspection can also help you determine whether your septic tank is the correct size for your household.

What are the disadvantages of a septic tank?

While septic tanks offer some great benefits, they can come with some drawbacks as well. It’s important to keep these in mind when considering if a septic tank is right for your home.

Clogged Drains

Like any plumbing system, a septic tank can experience issues with blocked drains if homeowners don’t take the proper precautions. Items that should never be flushed include cigarette butts (despite their softness, they aren’t meant to pass through toilet siphons) and paper towels (they’re thick enough to cause a blockage in toilet pipes). It is also wise to avoid putting foreign objects into the drains, such as cotton balls or feminine hygiene products. Likewise, automotive chemicals should never be flushed, as they contain toxins and can damage the septic tank.

In addition, a septic tank can become overloaded if non-food waste is dumped into the drains. In such cases, the septic tank may need to be pumped. This can be a costly maintenance expense, and it’s important to be mindful of what goes down the drains.


A septic tank can be more expensive to install than connecting to the city’s sewer line. However, it saves homeowners money on monthly water and sewer bills. It’s also a better option for environmentally conscious homes.


Depending on what type of septic tank you have, it can last for decades if properly maintained. Septic tanks made from concrete or steel are extremely durable and can often remain intact for up to 40 years. However, if the septic tank is abused or improperly maintained, it could need to be replaced sooner than expected.

Environmentally friendly

Septic tanks cut pollution by removing bacteria from wastewater before it enters the soil. They also help nearby flora and fauna by recycling water that is naturally absorbed by the surrounding soil.

A septic tank can pollute the environment if it’s not properly inspected and maintained. Without regular professional septic tank inspections and pumping, the tank can leak toxic substances into the soil and groundwater. It’s crucial that homeowners schedule these services to ensure they get the most from their septic tank and protect the surrounding ecosystem.