What Is a Mound Septic System?

A mound septic system is a specially designed wastewater treatment system used when the site conditions—like poor soil drainage or high groundwater—make a traditional (conventional) drain field unsuitable. Instead of using the natural soil alone to treat effluent, a mound system elevates and enhances the drain field to ensure proper treatment and safe disposal.

Why You Might Need a Mound System

Mound systems are typically required when:

  • The soil has poor permeability, such as heavy clay.

  • The seasonal water table is high, risking groundwater contamination.

  • There’s shallow bedrock or restrictive layers near the surface.

Before installation, a site evaluation and soil test are required to determine whether a mound system is the best option.

How a Mound Septic System Works

A mound system is more complex than a conventional system, but the basic process is similar:

  1. Septic Tank

    • Just like in a conventional system, wastewater first flows into a septic tank, where solids settle and begin to break down.

  2. Pump Chamber

    • Treated liquid effluent flows into a separate pump chamber. This chamber regulates the flow and pumps the effluent up to the mound.

  3. Mound and Distribution System

    • The mound is constructed from layers of sand, gravel, and soil, and raised above the natural grade.

    • A network of perforated pipes distributes the effluent evenly across the top layer of sand.

    • The effluent slowly trickles down through the sand and into the natural soil, where it undergoes further treatment.

Key Components of a Mound System

  • Sand Layer: Provides additional filtration and treatment.

  • Gravel Bed with Distribution Pipes: Spreads the effluent evenly.

  • Soil Cover: Helps protect the mound and blend it with the landscape.

Maintenance Tips for Mound Systems

Because mound systems are more complex, they also require a bit more care:

  • Regular pumping of the septic tank (every 3 years your county will send a notice for required maintenance).

  • Annual maintenance to flush the distribution system.

  • Don’t flush non-biodegradable items (like wipes, feminine products, or grease).

  • Water conservation is crucial—mound systems can be sensitive to overloading.

  • Protect the mound area by keeping it clear of heavy vehicles, buildings, livestock (should not be in a livestock pasture) and deep-rooted plants or trees.

Advantages and Considerations

Pros:

  • Ideal for sites with challenging soil or drainage issues.

  • Protects groundwater by elevating the drainfield.

  • Provides a long-term, code-compliant solution in difficult locations.

Cons:

  • Typically more expensive to install than conventional systems.

  • Requires electricity for the pump and more frequent inspections.

  • Visibly raised mound may affect landscaping aesthetics.

Is a Mound System Right for You?

If your soil isn’t suitable for a conventional septic system, a mound system could be a reliable and environmentally safe solution. While installation and maintenance are a bit more involved, proper design and care can keep your mound system working efficiently for many years.

Not sure what type of system you need? Contact us for a site evaluation or soil test—we’ll help you find the best fit for your property.