What is the purpose of a leach field in a septic system?

The primary purpose of a leach field, also known as a drain field or absorption field, is to distribute liquid waste safely into the ground. After wastewater exits the septic tank, it contains a mixture of partially treated liquid and small amounts of solid matter. Within the leach field, this wastewater is dispersed through a network of perforated pipes placed in trenches filled with gravel or stone.

As the liquid seeps into the surrounding soil, it undergoes natural filtration and is treated by microbial activity in the soil, which further breaks down harmful pathogens and organic matter. This process not only helps to safely return treated wastewater back to the environment but also prevents contamination of groundwater.

Other options focus on different aspects of septic system functions. For instance, one option mentions storing treated wastewater, which occurs in the septic tank, not in the leach field. Another option describes the collection of solids, which is also the role of the septic tank, where most solid waste is separated and held. The mention of holding chemicals for treatment does not apply as leach fields function to manage biological treatment through soil interaction rather than chemical storage. Thus, distributing liquid waste safely into the ground is indeed the correct and essential role of the leach field in septic systems.