What is a Mound Septic System? | Pros and Cons of Mound Septic System

A septic system is an underground effluent treatment system that is most commonly used in rural areas. These systems are most commonly used all over the world. The septic systems are usually employed in areas that don’t have a connection with the sewerage system. There are multiple types of septic systems, and the mound septic system is one of them. This article the mound septic system working, components, and its installation cost.

What is a Mound Septic System?

A mound septic system is an underground wastewater treatment system used to treat wastewater in areas where multi-stage wastewater treatment systems are limited.

These systems are used as substitutes for the drainage field of traditional rural septic systems. The mound septic systems are most commonly used in areas in which septic tank systems are susceptible to failure due to highly impermeable or permeable soils, shallow-pored bedrock soils, and high groundwater terrain.

mound septic system, mound system

In the 1930s, the North Dakota College of Agriculture developed the first mound septic system. In the 1976s, the mound system design was studied by the University of Wisconsin as a part of the university’s waste management project. This project published the 1st design manual to determine the design conditions and criteria for the correct location of the mound. A new manual was published in the 2000s.

A mound septic system needs a more complex design than standard systems. It also requires more electrical and other components than standard systems. It has a layer of gravel over a few meters of sand.

After installing the mound system, covers it with soil and plant grass. It also has water division tubes that fix in the gravel layer and a pump container that gathers the effluent coming from the tank. This container delivers the effluent to the drain field.

The container also has an alarm system that notifies the owner or service company if there are pumping problems inside the container.  

The mound septic system has less service life than the service life of the standardized septic systems.

How Does a Mound Septic System Work?

A mound septic system is employed in areas where conventional septic tank systems are not ideal for use.

For example, there may be too much clay in the soil for the water to penetrate at sufficient speed, or the water table may be too close to the surface. The mound system has an absorption mound, a dosing room, and a septic tank. A mound system works very similarly to other septic systems.

Mound Septic System Working

During the working of the mound septic system, firstly, the wastewater flows from your house into the septic tank.

As the wastewater reaches the septic tank, the tank traps the wastewater for a long time so that solid particles can settle down. After this, the wastewater flows by the septic tank into the dosing chamber.

The wastewater is stored in this chamber and regularly pumped into a mound of soil. This mound offers a sufficient layer of soil with sufficient thickness to ensure that there is enough time and space to treat the wastewater adequately.

During this process, the soil traps and absorbs the wastewater bacteria, and microorganisms decompose these bacteria. This process is known as the purification process. This process eliminates most nutrients (excluding nitrogen and some salts), organic matter, and pathogenic organisms. As the soil in the drain field is flooded, some of its wastewater treatment capacity is lost.

After completing the purification process, the purified effluent evaporates from the soil or ends up in the groundwater. The vegetation that grows on the mound system helps to evaporate some of the fluid. This is especially important in locations with a low water table.

Due to these features, mound systems work more efficiently and have long service life than conventional systems.

Components of Mound Septic System

The mound septic system has the following major components:

  1. Septic tank
  2. Dosing chamber
  3. Drain field
  4. Soil

Mound System components

1) Septic Tank

A septic tank is a buried watertight chamber. Polyethylene, fiberglass, or concrete is usually employed to make a septic tank.

As the sewer water enters the septic tank, it traps this sewer water for a long time so that the solid particles settle down. As it traps the wastewater, the sludge, greases, and oils also float on the water’s surface. It also permits the fractional decomposition of solid particles.

Read More: Septic Tank Working and Types

2) Distribution Chamber

The distribution chamber pulls the wastewater out of your septic tank and delivers it to the drain field. The component of the mound septic system assists you in making sure that the wastewater is evenly delivered to the drainage area.

It has many septic tank openings that direct to the drain field. If the septic system dosing chamber does not work correctly, the water distribution will be uneven and cause poor drainage.

3) Leach Field 

After passing through the septic tank, the wastewater delivers to the leach field or drain field for subsequent soil treatment. Every time new sewer water enters the septic tank, some treated sewer water pushes into the leaching/drainage point for more treatment.

The most famous drain fields consist of a sequence of trenches surrounded by septic gravel or rock and containing perforated pipes covered with dirt and mesh. Drainage that gets into the drain field is partially evaporated and partially absorbed by the soil.

4) Soil

The sewer water from the septic tank flows into the drainage system, where it penetrates the soil. This soil removes harmful nutrients, viruses, and bacteria for final cleaning. The availability of sufficient soil is very important for successful wastewater treatment.

How much does a Mound Septic System cost

A mound septic system has a high cost compared to a conventional septic system because it requires a more complex design. The price of the sand and electric pump also affects the total cost of this system.

The average cost of a mound septic tank system is anywhere from $9000 to $20,100. In contrast, conventional septic tank systems are relatively inexpensive, averaging from $2900 to $15,000.

  • The average costs of the mound septic systems are from $9000-20,000 but can be high, especially for large systems.
  • Regular maintenance of wastewater treatment plants is essential, with an average annual pumping and maintenance cost of approximately $500.

Mound Septic System Problems

The common problems of the mound septic systems are given below:

1) Failure due to poor design 

  • The mound is positioned on the soil with a minimum of 1-foot soil above the intermittently saturated soil.
  • Inadequate sand to treat sewage pollutants preceding native soils (toes)
  • The mound septic system is located on compacted or unsettled soil (toe/top)
  • The soil treatment system is not on the contour lines
  • The soil treatment system located in the plateau/swales drainage path
  • Incorrect estimates of soil permeability and structure or texture
  • Incline calculation error (a system designed for flat fields, not for slope fields) (toes)
  • Calculation error absorption area/lower area: the area where wastewater comes in the original soil (toe/top). This problem can occur due to heavy clays, which typically require large absorption areas and low counter loads.
  • When stacking various mounds on the slope, with insufficient space between the two

2) Poor Construction 

Installation-related construction faults are given below:

  • Reduces the penetration of the plant mat as additional vegetation is not detached (toe)
  • The wastewater receiving area is compressed during construction, decreasing intrusion (toe)
  • Water stays in loose pipes and freezes during winter sessions (pump tank or side problems)
  • During the scarification or drilling process, the manure receiving area is contaminated because the soil moisture has exceeded the plastic confine (toe).
  • Wrong pump selection or float setting (toe or side/top)
  • Leaking parts of the water tank (toe)
  • Broken or disconnected pipe (tip or side)

3) Failure due to Misuse 

  • Septic tank overturned because of excessive use of detergents, chemicals, and medicines (top/ side)
  • Leaky joints or excessive use of water (toe)
  • Clean water sources connected to mound septic system, such as sink Pumps (Toes)
  • Drainage from the roof or the impermeable area of ​​the septic tank or the system area (toe).
  • Deficiency of pumping solids from septic tanks or other heavy waste (top/side)
  • Inadequate landscaping leads to a compaction of the system’s surroundings (toe)

Maintenance of Mound Septic System

  • If you haven’t connected your mound septic system with observation pipes, it is suggested that you should install them immediately. Observation pipes remove the necessity for the unearthing and elimination of the access ports to inspect the septic tank.
  • Encourage routine inspections of the dosing chamber through an observation tube. If the water depth is gradually increasing, there may be a problem.
  • The dosing chamber and septic tank must be evacuated every 3-5 years. According to the septic tank size and the number of households, the tank pumping intervals may vary. The septic tank should regularly inspect each year to determine the rate of sludge buildup.
  • Plant grass and other vegetative covers on the drainage area to increase water uptake and stop erosion. However, do not plant trees or bushes with many roots in or near the drain, as this can clog the drain tubes.
  • Don’t construct or derive vehicles on the drainage area. This can compress the soil, reduce its absorption ability and damage the distribution tubes.
  • A small lawnmower may use to cut grass in the drainage area. But, do not install permanent devices such as playground equipment on the mound septic system. e
  • Keep a layout sketch of your mound septic system that represents the location of the drain field, dosing container, and septic tank in your home.
  • Take measures to decrease the use of water in your home and keep unwanted solids such as paper, plastic, and food out of your drainage system.
  • Do not drain solvents, toxic chemicals, grease, or oil. These materials can damage the system.
  • The exit of wastewater from a house drainage ditch must be guided away from the underground absorption point.

Advantages and Disadvantages of Mound Septic System

Advantages of Mound Septic System

  • It can be installed anywhere.
  • It doesn’t need a separate container.
  • These systems have an easy installation than other types of systems.
  • The mound septic system doesn’t require a large installation area. 
  • It requires very low maintenance.
  • The installation of the mound system reduces the risk of groundwater contamination.

Disadvantages of Mound System

  • This system has a high installation cost.
  • It can’t install the areas which have limited space.
  • It has high price than a conventional septic system.
  • If there will be any leakage then you will need to rebuild the mound partially or fully.

FAQ Section

Who invented the septic system?

In the 1860s, Jean-Louis Mouras invented the septic system.

Is a mound septic system bad?

  • A mound system requires a high cost for installation
  • It can’t use in areas which has space problems
  • It doesn’t have a container for sewage water storage. Therefore, it requires a large area for trench

How long does a mound septic system last?

A mound septic system has a service life of 15 to 40 years.

Can a mound system be put anywhere?

Yes, these systems can be installed anywhere but these have a high cost for installation. But these systems can’t be installed in locations that have limited space.

Can I walk on a septic mound?

Generally, it is not advisable to walk on a septic mound. The mound is engineered to bear the weight of soil and vegetation, but may not be designed to withstand a person’s weight. Stepping on the mound can lead to soil compaction and impair the septic system’s capacity to process and dispose of wastewater effectively.

Do mound septic systems smell?

Septic mound systems are engineered to efficiently manage and eliminate wastewater, which generally means they should not release any noticeable smells. Nevertheless, in uncommon instances, specific problems may occur, resulting in the emission of an unfriendly smell from the septic mound.

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  5. Good info, however towards the top you say, “The mound septic system has less service life than the service life of the standardized septic systems.” Then the end of the how it works section you say, “Due to these features, mound systems work more efficiently and has long service life than conventional systems.” Seem to be a contradiction. Can you clarify which it is?

    • Thanks for informing me.
      I wanna let you know that Mound systems work more efficiently and has long service life than conventional systems because it has more advance features than the conventional system.

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