Which color marks sanitary sewer systems?

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

Answer: (A)

When teams plan digging work, they rely on color codes painted or marked on the ground to identify what's below. This helps prevent damage to underground utilities and keeps workers safe. Green is the color used to indicate sanitary sewer lines (and often associated storm drainage). That’s why green is the best choice for marking sanitary sewer systems. Other colors serve different purposes—blue is typically potable water, purple is reclaimed water, and red marks electrical lines—so they wouldn’t indicate a sewer. If you’re ever digging, always verify with local utility maps and call your regional underground-location service before starting.