How deep should effluent be below the soil surface in a drain field?

The correct answer indicates that effluent in a drain field should be between 12 to 18 inches below the soil surface. This depth is crucial for ensuring proper treatment and absorption of the wastewater as it percolates through the soil layers.

At this depth, the effluent is adequately aerated by the soil, which allows for effective microbial action to break down contaminants. Additionally, being within this range helps to prevent surface pooling of wastewater and minimizes the risk of contamination to surface water or groundwater.

The soil composition and its ability to filter and treat the effluent also play a significant role in determining the appropriate depth. If the effluent were placed too shallow, there could be insufficient soil treatment, while placing it too deep could reduce the efficiency of the system and inhibit proper drainage. The 12 to 18 inches range strikes a balance that promotes optimal functioning of the drainage field while protecting the surrounding environment.