Where possible, sewer lines shall be located a minimum of __ horizontally from, and ___ vertically above any potable water supply line

• A. 8 ft, 3 ft
• B. 10 ft, 2 ft
• C. 9 ft, 3 ft
• D. 9 ft, 2 ft

Answer: (D)

Protecting drinking water from potential sewer contamination relies on keeping sewer lines cleanly separated both horizontally and vertically from potable water lines. The minimum horizontal clearance of 9 feet provides a substantial buffer so that construction, settlement, or leaks in trenches are unlikely to affect the water line. The vertical separation of 2 feet ensures an added gap in the vertical direction, reducing the chance that any seepage or backflow from the sewer could reach the potable water line. This combination—9 feet apart side-to-side and 2 feet in the vertical plane—best meets the safety intent. Other options fall short either on horizontal distance or vertical offset, so they don’t provide the same level of protection.