According to code, how thick should the filter material over drain lines in disposal fields and trenches be at a minimum?

The minimum thickness of the filter material over drain lines in disposal fields and trenches is specified to be 2 inches in accordance with plumbing codes. This requirement ensures that there is adequate filtration while still allowing for proper drainage. The 2-inch thickness helps to prevent sediment and debris from entering the drain lines, which could potentially clog them and affect the efficiency of the drainage system. Additionally, this layer acts as a protective barrier that maintains the integrity of the disposal field or trench, facilitating effective wastewater treatment without causing drainage issues.