From California to Maine, and from Texas to Minnesota, more than 60 million people are being served by septic systems. A recent report shows that one in every three new homes rely on a decentralized septic system and so what looked like a temporary solution is now the norm.

Today, there are as many septic systems as there are soil types, and here in this post, we will show you each of the systems most commonly installed across the nation.

You will be able to learn about wastewater treatment, about the processes and components common to septic systems and also, about a variety of residential solutions that you may want to consider for your property.

  1. On-Site Evaluation 
  3. Why do we use pre-treatment units?
  4. Septic Tank
  5. Advanced Treatment Units (ATUs)
  7. Sand Filtration
  8. Recirculating Media Filters
  9. Constructed Wetland
  10. Disinfection Septic Systems
  13. Gravity-Flow Septic Systems
  14. Pressurized Septic Systems
  16. Conventional Drain Field
  17. Leaching Chambers
  18. Gravel-less pipe Septic Systems
  19. Evapotranspiration Bed
  21. Low-Pressure Dosing System
  22. Mound Systems
  23. Subsurface Drip Dispersal System 
  24. Spray Dispersal System
  25. Septic Installer in the U.S | Royal Flush Septics

Something that we’ve found interesting when putting this blog post together is that many people were unsure whether a septic tank should be regarded as a septic system or not.

In different words, is a septic tank the same as a septic system, and if not why?

As basic as this question may seem, it is so good that it has led us to reframe the structure of this content in a way that is both more specific and intuitive.

In short, both septic tanks and advanced treatment units (ATUs) are and aren’t septic systems. A little too confusing? 

Well, don’t worry, that is about to be solved for good. It is just a grammatical distraction that stands between you and the definitive answer. 

Since a system is a group of interacting entities that form a unified whole, saying that a septic tank is not a system is incorrect and just as false as saying that it is.

Why, because it takes more components, systems, and applications to accomplish the goal of conducting a proper and responsible wastewater treatment.

Since the goal of a septic system is to clean wastewater in compliance with environmental regulations and the respective social responsibilities, the context of a system is too big for a septic tank to fit on its own.

It is equally important to mention that a septic tank is responsible for providing an initial wastewater treatment that is critical to the overall process and for that reason, we refer to these systems as pre-treatment systems.

A septic system is then the combination of a pre-treatment system (septic tank or advanced treatment unit), a secondary treatment system, a transportation system, and a complimentary treatment system, which in this industry we know by the name of a land application system.

As small as this difference may seem, it is critical for understanding the general and specific scenarios that we will lay down for you on this blog.

Now that you are familiar with these ideas, you are more than ready to explore the type of pre-treatment units, secondary treatment systems, transportation systems, land applications, and resulting septic systems available for your consideration.

You will also notice that these systems do not only vary due to soil conditions but also sue to specific requirements, local legislation, and even weather conditions. 

Only an on-site evaluation will reveal most of the information required for a septic professional to be able to pair your property with an adequate septic system. 

On-Site Evaluation – Soil Evaluation |Royal Flush Septics

Now that you know why a site evaluation is important, what can you expect from one?

An on-site evaluation will dote the septic professional with details about the typography, the vegetation, the rainwater, the location of other water masses, the volume of wastewater generated, and specific characteristics of the soil like:

a. The texture of the soil.

b. The <a> transport rate </a> (the ability of layers to transport water)

All of this information is then submitted for examination and used to determine the design requirements and considerations relevant to the overall design and installation.


Why do we use pre-treatment units?

Not only do pre-treatment units allow secondary treatment to be more effective, but it also removes the solids and materials that the bacteria in the media filter and the soil is not capable of digesting or decomposing.

That means, that without a primary treatment, there would be particles in the wastewater that will endure and compromise the system and the safety of the environment. 

Another important reason to use pre-treatment units is that the effluent is better treated, mild, consistent and it also flows easier through the system and the soil which is crucial for performance.

Since we understand how crucial a role pre-treatment units play on the septic landscape, let’s take a look at the couple of options that we can pick from. 

Septic Tank

Unlike a dedicated septic system, a septic tank is just an enclosed and watertight container commonly of one or two compartments, capable of separating solids in the raw wastewater entering the system. 

The main objective of the septic tank is to settle the heavy solids, blow the greases and low-density substances to the top, remove inorganic matter and filter out anything that would compromise the system as a whole.

Advanced Treatment Units (ATUs)

An advanced treatment unit or aerobic treatment unit is a more rigorous and exemplary version of our previous conventional septic tank. 

The quality of the effluent of these systems is comparable to that of the municipal wastewater treatment units only on a much smaller scale.

What else is inside of an advanced treatment unit? Well, four basic processes are going on inside. A couple of which we should be able to recognize from our previous discussion on septic tanks.

The first process occurs in the permanent tank or trash tank and consists of removing the materials that microbes cannot degrade.

The second process takes place in the aeration chamber. With the help of an air pump, piping, and diffusers air is forced inside of the aeration chamber to intensify the biological principle upon which pre-treatment units are built.

In the conventional septic tank, this process also takes place but at a much slower pace given the lack of air in the system. 

A settling chamber or clarifier is the third process, and it allows microbes to settle out and includes a method to return bacteria to the aeration system.

Finally, the Land application system distributes the partially treated wastewater into the soil, where the naturally occurring microbial activity will remove the remnants in the effluent and let the water to recover its state as it leaves the land application field and settles on in the water reservoir.

Since a diverse and active population of microbes is required to break down solids in the tank, septic maintenance should be conducted in discrete periods and not as often as one could initially suppose.


As previously discussed, septic tanks and ATUs are not capable or even intended to provide the rigorous treatment that is expected from residents, homeowners, and homebuilders in the nation. Here, we will review the secondary treatment systems employed to fulfill those requirements.

Sand Filtration

Sand filtration systems are not too strange for us. In appearance, they are very similar to the sandbox many of us have played in as kids but if you don’t know what I am talking about, you can just think of it as a pool filled with sand instead of water. 

Not just any kind of sand though, we are speaking of a combination of sands and other materials with a specific size, array, and pattern to ease the filtering process.

The result is a tank or box with layers of solids of different sizes and nature that combined will effectively treat the remnants trapped in the effluent as it flows downwards.

A typical system consists of a septic tank (primary treatment or pre-treatment unit), a dosing tank, a sand filter (secondary treatment), and a land application system (final treatment). 

The sand filter box can be both constructed (i.e: with concrete) or excavated and lined with plastic. As for the content, we’ve already spoken about the composition of the media bed (different sands, gravel, etc) and a collection pipe intended precisely to recover the effluent after treatment.

After being transported to the land application system to receive final treatment, that effluent will then settle in the well. 

Sand filters can be constructed either above or below the ground for easier access or seamless landscape integration respectively. 

Recirculating Media Filters

After having introduced you to sand filtration systems, speaking about these systems will be much easier.

Like the previous example, these also rely on a septic tank, a media filter with pretty much the same principle as the sand filter, and a land application system. One detail about these systems, however, changes the dynamic completely. 

These systems have a recirculating mechanism that consists of relatively small-diameter piping and a pump that recirculates the effluent before it exits the septic tank. 

This additional step aerates the wastewater which increases the bacterial process and provides better primary treatment and at the same time, it also filters the wastewater as it flows down the media.

The media filters are a composition of sand, gravel, plastic, pit, foam, and fabric of different sizes used to provide adequate treatment. Why using one media instead of another or a combination of them? 

Well, it depends on the volume of wastewater and the quality of effluent required. As for why using media filters at all, they are simply advantageous because microbes thrive on the surface of the media and those microbes feed on the nutrients, pathogens, and solids that we want to get rid of. 

After the wastewater is recirculated and pumped back into the septic tank, it is then sent to the land application system for further treatment.

Constructed Wetland

A constructed wetland is a remix of nature’s unique way of cleaning water. This precise process is arguably the most critical to the sustain of life on our planet and certainly critical to our survival.

These systems naturally rely on a vast number of microorganisms that also depend on those nutrients to survive. Lurking on the subsurface of the soil, these starving microorganisms support the earth’s objective to treat wastewater and fully restore its properties.

Similarly, the artificial form of this process generally known as “constructed” wetland is no more than a man-made compressed version of a much larger and complex organic process.

Just like the earth depends on different types of microorganisms to treat water, a constructed wetland performance is highly conditioned not only by the properties of the soil but the plants and vegetation thriving in the area.

The only difference is that in nature, these systems are bigger and visible, while in a residential constructed wetland, the water flow is maintained at a subsurface level.

These systems are designed to blend and enhance the landscape design. This is relatively easy given the possibility of using grated stone, aquatic plants, and other types of vegetation that are compatible with the system and the landscape. 

The most important consideration for the selection of the plants to be used in the system is that they can survive in a saturated medium, which is the case of many hard tissue plants that at the same time aerate the soil during winter, which is relevant for proper working conditions.

A constructed wetland consists of a pre-treatment unit (septic tank or ATU), a constructed wetland bed (secondary treatment), and a land application system. 

Since we are familiar with the majority of the components, all that is left to clarify is that the wetland can be constructed with PVC or any potential permeable substance (watertight) or they can be also excavated on the soil if the content of clay is high. 

Disinfection septic systems

These systems are used as an additional safeguard against pathogens and are placed between a secondary treatment unit and a land application system.

Although the most basic, common, and affordable disinfection method is through chlorinated tablets (solid), there is also the possibility of employing UV light or ozone, which is very common in larger wastewater treatment facilities and Municipal Wastewater treatment systems.


Common to all of the systems presented in this article, a land application system is both critical for the installation and the treatment of the effluent.

The soil acts as a final stage of treatment, it naturally cleanses the water with no chemicals or products required. 

Microbes in the soil remove the remaining organic matter, nutrients, solids, and pathogens in the water.

The type of land application system you can use depends on your site condition, the type, and depth of the soil available for treatment, all of which will be determined during the <a> on-site evaluation </a>.


As obvious as it might sound, transportation systems are required to move water from pre-treatment systems into the soil and they shall not be given for granted.

They are crucial to the overall process. Each of the subsystems and components they are connected to is conceived to be sealed and watertight, all of which could be compromised if transportation systems were not properly addressed.

Transportation systems are a guarantee of safe operation and environmental compliance. Given their relative simplicity, making sure that every detail is properly addressed will remain crucial to our role as septic professionals.

Depending on seasonal and on-site conditions, fluids may or may not require the presence of auxiliary equipment to force the effluent through the piping. 

With that logic, the following two subcategories will be sufficient to explain where transportation systems fit on the septic landscape. 

Gravity-Flow Septic Systems

In the first category, we have those soils whose conditions have the potential capacity to exert enough pressure on the effluent for it to be transported into the land application system.

Pressurized Septic Systems

For those cases in which the first is not possible or viable, we use pressurized systems.

Whenever the characteristics of the soil do not exert the required amount of pressure onto the fluid for it to travel through the piping, auxiliary equipment with the capacity to compensate for that is installed.

What are those characteristics? Well, it could be the depth of the soil, a shallow bedrock, or the proximity of a well or clean water masses.


Conventional drain field

As one of America’s first decentralized septic system, you may have seen or heard of these systems a couple of times in the past. 

As simple as they look, these systems proved to be effective for several decades that came before some of the most modern types of systems and components available today in the market.

These systems consist of a perforated pipe that follows a snake-like pattern on the area designated for treatment. While the holes around the circumference of the pipe ensure a drop-by-drop infiltration, it is the snake-like pattern that will later ensure optimal coverage and field absorption, which help us prevent soil saturation and malfunctioning.

Surrounding those perforated pipes, a layer of gravel and media filters provide a secondary treatment before the effluent coming from the tank goes into the soil.

The gravel surrounding the pipes will store the wastewater until it cannot be absorbed by the soil and so in this sense, the system regulates this process even further.

At this point, the microbes on the subsurface will not only decompose the waste, but they will also provide us with an extra layer of protection against soil saturation. 

How is that even possible?

Well, as the microorganism feed on the nutrients, pathogens, and suspended solids in the effluent, they leave a byproduct which is accumulated around the gravel, that is both on top and bottom of the drain field given the circumference of the pipe and that organic mat slows down the water movement.

In a conventional drain field, the process closes with the water being utilized and purified by the grass growing on the soil subsurface and above of the constructed wetland. That is how important vegetation and plants are to the adequate functioning of these systems.

Leaching Chambers

Alternatively to the pipes and gravel systems described above, these chambers do not require very particular soil conditions to work properly. 

Because these chambers are embedded within trenches previously carved on the field and stacked between the media and the soil, they are considered to be somewhat permeable.

The wastewater running from the tank is held within the spacious room left inside the chambers until it can be moved and infiltrated into the soil.

An added advantage of these systems is that their basic shapes allow the installation to be more flexible and follow the perimeter and contour of the terrain with a certain ease.

Gravel-less pipe Septic Systems

In the wide range of septic solutions, there aren’t many systems like this. They are designed to work without gravel and similar materials and for that reason, they are one of the most popular alternatives to media field trenches. 

These singular systems are built to be completely sealed, and treat the wastewater within the piping. 

The chief advantage is that the pipe is flexible and that can fit elevations and contours easily. Fitting specific elevations.

The fabric surrounding the corrugated pipe allows for wastewater to distribute evenly around the circumference of the pipe and it also prevents the backfield from entering the discharge holes of the pipe.

To use these transportation systems, it is required that the septic system is being installed on well-aerated soil to prevent the build-up of the biological mat on the geotextile fabric wrap and malfunctioning.

Evapotranspiration bed

As you might be able to describe from the name of these systems, they rely on the evaporation of the wastewater, being more precise, on the transpiration of plants arranged above the bed conveniently installed to favor the ideal working conditions.

These systems are commonly installed in areas where the bedrock is too shallow and so treating the wastewater before it reaches the groundwater may be challenging.

Also, in areas where the structure of the soil and other conditions (such as weather or seasonal conditions) will not allow the wastewater to move through the soil as it is supposed to.

A singularity of these septic systems is that they offer the possibility of being lined or unlined depending on the soil conditions to better fit that profile. 

After an on-site evaluation, the engineers and the septic professionals will be able to make all the respective recommendations and fit those details on the septic design.


Low-pressure dosing system

For any pressurized system, there are at least two conditions that must be met. The first one is a clean, regenerative, and relatively large supply of the fluid required to enable a mechanism to transmit power from an initial point “A” to a final destination point “B.” 

The second aspect is the mechanism responsible for transmitting that power and depending on the size and nature of the operations it could consist of a simple pump and a tank to contain that fluid or an even larger compression room. 

The core of this system and the aspect that mainly separates it from the other systems that we have discussed up to this point are a pump tank and a network of small-diameter pipes placed in trenches.

The pump tank stores the water that the pump will dose into the drain field at the specified rate to avoid field saturation.

Another advantage of these systems is that the wastewater is distributed evenly across the system and onto the field, which facilitates optimal water absorption and increases the life of the land application system.

Mound systems

These systems are ideal for soil with minimal soil between the surface and either groundwater or bedrock. Given these conditions, there is no other option but to use a pressurized system that like in the previous case consists of a pump tank.

The difference between these systems and the previous low-pressure dosing systems is that in this case, the land application system changes.

A mound land has several layers of permeable field material, a sandy loam cap, and topsoil. Although there are minimal differences between the two systems, they both rely on microbes in the soil subsurface to provide proper wastewater treatment.

Subsurface drip dispersal system 

These systems not only provide an exemplary treatment if combined with the adequate pre-treatment unit, but they generally require much less space than conventional septic systems. 

The layout and the drip dispersal feature provide a uniform application of wastewater across the application field, which as you may have noticed, is one of the most critical factors to address during design and installation since the implications of an underperforming system will result in discomfort for the homeowners.

Aside from the pump tank common to all pressurized systems, these installations also require a filtration system, subsurface drip tubing, and a controller.

Remember, when it comes to reutilizing water, the requirement is a high-quality wastewater treatment and that is precisely why a filtration system and an optional disinfection system The filtration system and an optional disinfection system may be advised.

On the other hand, the controller is responsible for an automated and rigorous time-bound execution that, if performed correctly will reduce the water pressure before it enters the soil.

Spray dispersal system

Similarly to a drip dispersal system, the spray dispersal system is focused on reutilizing the water, and so, in this instance, the quality of the wastewater required for the system is the same. 

With a very similar if not precise list of components, the only difference between a drip dispersal septic system and a spray dispersal septic system is in the spray heads and any minor components required to sprinkle the water.

These long irrigation systems are amongst the most common applications in some of the commercial installations that you may visit with regularity and for that reason, they will look very familiar to you.

The sprinklers are configured to have a short trajectory and minimize drift from the spray area which falls on top of vegetation and landscape.

A controller is commonly installed to pivot between an on-demand spray or an HWL (high-water level) signal marking that the tank is “full” and increase the overall performance.

Septic Installer in the U.S | Royal Flush Septics

If you are located in the Dallas-Fort Worth Metroplex or any of the counties below, you can count on us for septic inspections, designs, and installations.

In the case that you are reading us from another city or county, you can get in touch with us to evaluate your case or we could help you find a septic designer in your area.