Factors That Determine the Cost of a Septic System Installation

System Size

The septic system's size determines labor and material costs, so sizing is a significant determinant of the overall cost. Septic sizing mainly depends on:

• The property's size
• The expected water use
• The local building codes

For example, a three-bedroom house usually requires a 1,000-gallon tank, which alone costs anywhere between $600 and $1,000.

System Type

Septic systems vary depending on how they treat waste. The common types include:

• A conventional system with a gravel drainfield that absorbs treated waste
• A chamber system where the drainfield has a series of chambers in direct contact with the soil
• An aerobic system where the septic tank receives oxygen injection to accelerate the decomposition process

Different systems require different materials, structures, and installation processes. Thus, your septic's cost will also depend on the type of system you choose. For example, aerobic systems are relatively expensive compared to most systems.

Tank Type

A septic system has a tank where the waste treatment occurs. The septic tank material also determines the system's cost. Common tank materials include:

• Concrete, with an average cost compared to other materials
• Plastic, which is relatively inexpensive
• Fiberglass, which is relatively expensive

Each of these materials has its pros and cons. For example, concrete is durable but can crack, while plastic is durable but can suffer damage during installation. Consider the pros and cons to help you make an informed choice.

Existing Landscaping

Septic system installation involves significant excavation - most parts of the system need to be underground. For example, excavation is necessary before the installation of the:

• Tank
• Drainfield
• Pipes
• Distribution box

The nature of the landscape will determine the excavation cost. The nature of the landscape depends on things like:

• Existing plants
• Existence or absence of rocks
• The gradient of the land

For example, you might spend extra funds to relocate existing plants to other areas.

Waste Flow

In all septic systems, the waste needs to flow from the treatment area to the disposal area. Waste flow can be via:

• Gravity, which is only possible if the treatment area (tank location) is higher relative to the disposal area drainfield
• Septic pump, which is necessary if the drainfield sits higher relative to the tank area or if the ground is flat

If you cannot use gravity, you need the septic pump, increasing the overall cost.

Aggregate Material Costs

The septic drainfield needs to have permeable materials to allow waste to percolate into the ground at the appropriate speed. Waste might accumulate on the drainfield if the drainfield is not permeable. An extremely permeable drainfield can allow untreated waste into the ground.

You may need to excavate the drainfield and fill it with the right aggregate materials to get the right permeability. Gravel and sand are common options. In such a case, the cost of aggregate materials in your areas will also influence your price. For example, you may enjoy inexpensive materials if your area has abundant aggregate materials.

Note that your septic's installation will determine its operating efficiency and durability. O'Fallon Sewer Service has been in the plumbing industry for over 50 years. We have the experience to design, install, and maintain septic systems. Contact us for a quote on any septic service you need. We look forward to hearing from and speaking with you.