What is the term used to describe the rate at which water moves through soil?

The term "percolation rate" specifically refers to the speed at which water moves through soil, primarily measured during percolation tests which assess soil's ability to transmit water. Understanding percolation is crucial for septic system design, as it directly impacts how well effluent can filter into the surrounding soil and be treated before reaching the groundwater. A higher percolation rate indicates that water moves quickly through the soil, which may affect the sizing and positioning of septic system components.

In context, while absorption capacity deals with how much water the soil can retain, and infiltration rate describes the process of water entering the soil surface, both are related concepts but do not focus solely on the movement of water through the soil in the way percolation does. Drainage rate similarly measures the speed of water leaving the soil but is not as specifically tied to the rate of movement through different soil layers. Thus, percolation rate is the most precise term for this phenomenon in septic systems.