What material should surround field distribution piping, according to standard practice?

The use of washed gravel, ranging from ¾ inch to 2 ½ inches, as the surrounding material for field distribution piping is based on its ability to promote effective drainage and aeration while reducing the likelihood of clogging. Washed gravel provides sufficient void space for water to flow freely, which is critical for maintaining the functionality of the distribution system in wastewater treatment. By reducing compaction, washed gravel helps ensure that effluent can move away from the piping and into the surrounding soil, thereby facilitating proper absorption and treatment.

Furthermore, the cleanliness of washed gravel minimizes the chance of introducing sediment or fine materials that could obstruct the perforations in the piping or hinder the distribution of wastewater. This choice enhances the longevity and efficiency of the wastewater system, making it the standard practice in field distribution piping design.