Final answer:
The grid system is the most commonly used pattern when laying out a leach field. It allows for efficient distribution of wastewater and easy maintenance.
Step-by-step explanation:
The pattern most commonly used when laying out a leach field is the grid system. In this system, the leach field is divided into equal-sized sections or grids, typically using pipes or trenches. Each section is then filled with a layer of gravel or stone and covered with a layer of soil.
The grid system allows for efficient distribution of wastewater throughout the leach field and provides uniform drainage. It also makes maintenance and repairs easier, as specific sections can be isolated and accessed for inspection or repair.
However, it is important to consider the topography and soil conditions of the site when implementing the grid system. Modifications may be necessary to ensure proper drainage and prevent water accumulation or saturation in specific areas.