The cost varies depending on the design criteria and the soil analysis. The least expensive systems are what we call the in-ground or gravity fed system. These have no mechanical pumps and do not require an above ground drain field or mound. These types of systems can cost from $5,000.00 to $8,000.00. The more expensive systems are alternative mound systems. These systems have a mechanical pump with alarm system and require a mound above ground because of the seasonal high water level. These types of alternative systems can cost $8,000.00 to $12,000.00 and more.