How to Build a Septic Tank

A septic tank is an essential component of a wastewater management system, commonly used in rural or suburban areas without centralized sewer systems. It is designed to safely process and dispose of household sewage and wastewater.

Understanding how to build a septic tank can be a valuable skill for those seeking a cost-effective and sustainable solution for wastewater treatment. This guide will provide an overview of the key steps, materials, and considerations involved in constructing a functional and reliable septic tank.

What is a Septic Tank and Its Function

A septic tank is a buried, water-tight container usually made of concrete, fiberglass, or polyethylene. It is a critical component of an on-site wastewater treatment system, designed to collect, treat, and dispose of sewage and waste generated from a household. The primary function of a septic tank is to separate solids and scum from wastewater through a process called sedimentation.

Solid waste settles at the bottom of the tank, forming sludge, while grease and lighter materials float to the top as scum. The partially treated liquid, or effluent, flows out of the tank into a drain field or leach field for further natural filtration and treatment within the soil. This process ensures safe disposal of wastewater, protecting the environment and preventing contamination of water sources.

Types of Septic Tanks

There are several septic tank design available, each with distinct materials, designs, and benefits to suit different needs and environmental conditions. Understanding the various types can help in selecting the most appropriate option for a specific property or usage.

Concrete Septic Tanks 

  These are the most common type of septic tanks, known for their durability and heavy weight. Concrete tanks are resistant to damage and have a long lifespan, often lasting decades if properly maintained. However, they can be more expensive to install due to their weight, which requires heavy machinery for placement.

Fiberglass Septic Tanks 

  Fiberglass tanks are lightweight, durable, and resistant to cracking and rust. They are easier to install compared to concrete tanks, but care must be taken to ensure proper placement, as they can shift in unstable soil. These tanks are ideal for areas with high groundwater levels or where weight is a concern.

Polyethylene (Plastic) Septic Tanks 

  Polyethylene tanks are becoming increasingly popular due to their lightweight and low-cost properties. They are highly resistant to corrosion and cracking, making them suitable for a wide range of environments. However, like fiberglass tanks, they may require secure installation to prevent shifting.

Steel Septic Tanks 

  Steel tanks were commonly used in the past but are now less popular due to their susceptibility to rust and short lifespan compared to other types. While they are strong initially, their tendency to corrode makes them less reliable over time.

10 Methods How to Build a Septic Tank

1. Planning and Permits

Before beginning construction, the first and most crucial step is to plan the septic tank installation thoroughly. This includes choosing the appropriate size for the tank, which depends on the number of people in the household and the average water usage. The size should also be in compliance with local health and safety regulations.

Depending on the area, you may need to obtain permits from the local health department or zoning office before proceeding. Additionally, it’s essential to assess the soil’s drainage capacity and ensure that the location of the septic tank complies with local setback requirements, which specify how far the tank must be from the home, wells, and property boundaries.

2. Selecting the Tank Design

There are different designs and materials for septic tanks, and selecting the right one is vital for ensuring the system’s effectiveness. The most common designs include concrete, fiberglass, or plastic tanks, with concrete being the most durable and widely used. Concrete tanks can be pre-cast or poured on-site.

Fiberglass and plastic tanks, though lighter and easier to transport, are not as long-lasting as concrete but are still reliable. Choose a design that suits your specific needs, considering factors such as soil type, local climate, and personal preferences.

3. Excavation for the Tank Site

Once the permits are obtained and the design chosen, the next step is excavation. This involves digging a hole large enough to accommodate the septic tank, taking into account the tank’s dimensions and additional space for plumbing and access. The hole should be dug carefully, making sure to level the bottom to prevent the tank from tilting once placed. The depth of the hole depends on the tank’s design and the ground’s natural slope.

4. Preparing the Foundation

Before placing the septic tank into the excavation, a stable foundation is essential. This foundation is usually made of compacted gravel or crushed stone, which helps to stabilize the tank and prevents it from shifting over time. The gravel also allows water to flow away from the tank and promotes proper drainage. Once the base material is spread evenly in the excavated area, it should be compacted to ensure stability. If necessary, add additional layers of gravel to achieve the correct level and ensure that the base is smooth and solid.

5. Installing the Tank

Now that the excavation and foundation are complete, it’s time to install the septic tank. This step requires careful handling, as septic tanks can be very heavy, especially if made from concrete. If using a pre-cast tank, a crane or backhoe will be required to lift and position the tank into the prepared hole.

The tank should be placed evenly and level, ensuring that it sits firmly on the gravel base without any tilting. If pouring the tank on-site, the tank will be constructed in sections, and the concrete will need time to cure before the tank is fully installed.

6. Connecting the Inlet and Outlet Pipes

After the septic tank is positioned correctly, the next step is connecting the inlet and outlet pipes. The inlet pipe brings wastewater from the house to the tank, while the outlet pipe carries the treated water to the drain field. These pipes must be installed at a slight slope (typically 1/4 inch per foot) to promote the proper flow of water. For concrete tanks, use a core drill to create holes for the pipes and seal them with a waterproof adhesive or rubber gasket to prevent leaks.

7. Installing the Baffles

Baffles are essential components inside the septic tank that help control the flow of wastewater and ensure effective treatment. They prevent solids from exiting the tank too quickly and ensure that the water is properly filtered before moving to the drain field.

The baffles are typically made of concrete, PVC, or fiberglass, and they are placed at both the inlet and outlet ends of the tank. The inlet baffle slows down the incoming flow, allowing solids to settle at the bottom of the tank, while the outlet baffle ensures that the treated water exits in a controlled manner.

8. Backfilling Around the Tank

Once the tank is properly installed and the pipes and baffles are in place, it’s time to backfill around the tank. Begin by filling the space around the tank with soil, taking care not to damage the tank or disturb the plumbing.

Use clean, free-draining soil to ensure proper compaction and avoid the tank shifting over time. As you backfill, check the tank’s alignment and level, making adjustments as needed. The goal is to ensure that the tank remains stable and that there is no pressure on the walls.

9. Constructing the Drain Field

The drain field is a crucial part of the septic system that disperses the treated wastewater into the soil. The size and layout of the drain field depend on local regulations and the soil’s absorption rate.

The drain field typically consists of perforated pipes laid in trenches, which are then covered with gravel and soil. The pipes should be laid with a slight slope to ensure the water flows evenly. It’s important to ensure that the drain field is placed downhill from the septic tank to allow for gravity-assisted flow.

10. Final Inspection and Maintenance

Once the septic tank and drain field are in place, it’s time for a final inspection to ensure that everything is functioning properly. Local authorities may require an inspection to verify that the system meets all regulatory standards.

After passing inspection, the septic tank should be periodically maintained to ensure long-term functionality. This includes regular pumping to remove accumulated solids, checking for any cracks or leaks in the tank, and ensuring that the drain field remains unobstructed. Proper maintenance is essential for prolonging the lifespan of the septic system and preventing costly repairs in the future.

Conclusion

Building a septic tank is a significant undertaking that requires meticulous planning, knowledge of plumbing, and attention to detail. While the construction of a septic system is a manageable project for those with experience, it is highly recommended to consult or hire a professional to ensure that the system meets all local building codes and safety standards. Thanks for reading, and we hope this has given you some inspiration on how to build a septic tank!