What minimum size perforated pipe shall be used in a gray water irrigation system?

• A. 1 1/2 inch
• B. 2 2/2 Inches
• C. 3 inches
• D. 2 Inches

Answer: (C)

In gray water irrigation, the pipe size you choose directly affects how much water can move through the system and how likely the line is to clog from solids in the gray water. A perforated pipe with a 3-inch diameter provides enough cross-sectional area to carry typical residential graywater flows without developing high velocities that can push solids into the perforations or cause uneven distribution. The larger size also makes maintenance easier and reduces the chance of clogging, helping water disperse more evenly into the soil for effective irrigation. Smaller sizes, like 1 1/2 inches or 2 inches, are more prone to clogging and may not meet common design guidelines for graywater distribution, leading to reduced performance.