Types of Septic Systems

septic tankA septic system not only includes things we see every day, such as the sinks, showers, tubs, toilets, drains and pipes within your home, but also the several outside and underground parts that some people never see and often forget and sometimes even neglect. That is an issue that brings us to the different types of septic systems. We will discuss mostly those parts that you don’t see every day and explain their differences and how they work. That way you will be better equipped to make a decision for your home regarding its septic system needs.

There are over 25 different types of septic systems in all, so we will exclude some of the less popular types that you probably wouldn’t consider anyway. One of the main reasons there are so many types of septic systems is that there are many different soil conditions and most conventional septic systems rely on soil to filter the water from a septic system before it goes back into the ground water.

There are at least three main types of septic systems that you need to be aware of to make a decision for your home. The three main types are pressure distribution, standard gravity and advanced treatment. We will discuss where you would use each and why below.


    Effluent: When you send liquid waste into a septic tank, the same amount of liquid comes out of the exit pipe. The fluid exiting the septic tank and inside the tank is known as effluent.

    D-Box: Short for distribution box, a d-box is what is used to separate effluent leaving a septic tank to evenly distribute it to several pipes to carry it to the next stage of the process, the trenches.

    Trenches: The trenches are where the effluent goes from the d-box. There are several different types of trenches including drip irrigation drain fields, graveless chambers, and typical pipe and rock drain fields.

Standard Gravity Septic Systems

How an underground septic tank is connected to a house and leaching field.A standard gravity system is a fairly straitforward, non-proprietary system. The main thing you want to be aware of when distinguishing between the types of septic systems is the amount of good soil needed to filter the effluent.

A standard gravity system will require a minimum of three feet of good soil. Now, that doesn’t mean three feet from the surface; it means three feet from the point where the waste is expelled from the system. That point is already several feet underground, so in reality, you need three feet of good soil that is several feet underground.

In a standard gravity system, the waste water flows from the house to the septic tank where it starts breaking down. It then goes from the tank to the D-Box which directs the effluent to several trenches where the effluent is released to filter through the soil. The trenches need to below the septic tank for a standard gravity system to work; otherwise you would have a pump assisted gravity system.

Pressure Distribution Septic Systems

A pressure distribution system is another straight forward non proprietary design. It requires at least two feet of good soil beneath the trenches and is generally used when there is not enough good soil for a standard gravity system. The system usually uses a similar trench field to that of a standard system. The main difference is in the way that the effluence is delivered to the trench field.

In a pressure system, the effluence is transported to the trenches in a small PVC pipe and is released to the trenches under pressure, allowing the entire trench field to be wetted at the same time. This way more area of soil is used to filter the effluence so that less soil depth is needed overall.

Advanced Treatment Septic Systems

Advanced treatment septic systems are a completely different animal from the other two types in this article. Many of them are proprietary with brand names, but some are non proprietary systems. These systems are required when there are shallow soil conditions present.

The amount of good soil required to filter an advanced system range from 12 to 30 inches. These types of systems often involve a pressurized drainage system similar to that of a pressure distribution system. The main difference is in where the effluence is filtered after leaving the septic tank.

There are several types of filtering systems used to cleanse the effluence before releasing it back into the environment including sand filters, sand mounds and aerobic treatment systems.

The details of the different types of advanced treatment systems are beyond the scope of this article, but the important thing is to be aware of the main types of septic systems so you can make a more informed decision for your home.

We hope that this article has given you some insight into the wide range septic systems. There are many other types of systems and much more to be learned, but this page is meant as introductory material to introduce you to some of the more popular types of septic systems that you are likely to encounter while searching for the proper one for a new home or a replacement for an existing system. Also, now you should be able to understand some of the parts involved and at least know how to speak correctly to a contractor or perhaps even do some minor maintenance by yourself.