North Carolina Septic Inspector Exam 2 Practice Test

What is the main function of the drainfield trenches in a septic system?

To filter solids from effluent before entering trenches. To store treated effluent for reuse. To receive effluent from the distribution box and allow it to infiltrate into soil. To monitor groundwater near the drainfield.

Correct Answer:

To receive effluent from the distribution box and allow it to infiltrate into soil.

Explanation:

The drainfield trenches are where the liquid effluent from the septic tank is distributed into the soil. Through perforated pipes in gravel-filled trenches, the liquid enters the surrounding soil and gradually infiltrates. The soil then provides filtration and microbial treatment, breaking down organic matter and reducing pollutants as the water disperses slowly, helping protect groundwater. Solids have already been separated in the tank, so the trench system’s job is not to filter solids or store treated wastewater, and monitoring groundwater is handled by separate measures rather than the trenches themselves.

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