Which component may be present in a drainfield system besides the septic tank?

• A. Gasket
• B. Backflow preventer
• C. Distribution box
• D. Vent stack

Answer: (C)

In a drainfield system after the septic tank, the water (effluent) is sent into a network of trenches, and a distribution box is used to split that flow evenly among the different trenches. This even distribution helps prevent overload in any single trench and promotes proper treatment of the wastewater in the field. The other items aren’t typical drainfield components: a gasket is just a general seal for pipe joints, a backflow preventer protects potable water lines, and a vent stack prevents sewer gases in the building’s plumbing—none are dedicated parts of the drainfield itself.