What color indicates Sanitary Sewer Systems?

• A. Red
• B. Yellow
• C. Green
• D. Blue

Answer: (C)

Understanding color coding for underground utilities helps crews dig safely and protect infrastructure. Green marks indicate sanitary sewer systems—the pipes that carry wastewater from buildings to treatment facilities. This color coding guides workers to avoid cutting or damaging those lines and to follow the appropriate procedures when excavating near them. For context, blue typically marks potable water lines, red electrical power lines, and yellow gas lines; purple is used for reclaimed water, and pink for temporary survey marks. While exact schemes can vary by locale, green as the signal for sanitary sewer is a common and widely used convention in the industry.