The most significant factors that affect the cost of installing a septic system are usually the system layout and the tank chosen. Location plays a major role in determining the layout of the system. For example, a steep slope may require a tiered leech field, which is more expensive. Additionally, the size of the tank and the material it is made of affect the cost of the system itself as well as the labor cost involved in the installation.
Certain climates and ground conditions may require more expensive septic systems. For example, an evapotranspiration system can be around eight times more costly than a standard gravity system; however, it may be a better choice for a desert home. Similarly, soil with poor absorption qualities may also necessitate a more expensive system. If the property is in an area with a high water table, a more customized design may be necessary.
A large number of trees in the area can also increase the cost of installation, because their roots may interfere with the placement and proper operation of the system.
Placing a septic system is fairly labor intensive, so the local cost of labor can play a major role in determining the cost of installation. Regulatory factors such as permits and excavation requirements may also affect the cost.