What is the minimum distance between the top of the sewer line and the bottom of a water line where they cross?

What is the minimum distance between the top of the sewer line and the bottom of a water line where they cross?

• A. 6 inches
• B. 15 inches
• C. 12 inches
• D. 18 inches

Answer: (C)

The main idea is to prevent cross-contamination between a sewer line and a potable water line. When they cross, keeping a vertical gap between them reduces the chance that sewage could backflow into the water supply or that gases and contaminants could migrate into the water line. The standard minimum clearance is twelve inches between the top of the sewer line and the bottom of the water line. If this spacing can’t be achieved, you’d need to reroute the pipes or install backflow prevention measures to protect the potable water.

The main idea is to prevent cross-contamination between a sewer line and a potable water line. When they cross, keeping a vertical gap between them reduces the chance that sewage could backflow into the water supply or that gases and contaminants could migrate into the water line. The standard minimum clearance is twelve inches between the top of the sewer line and the bottom of the water line. If this spacing can’t be achieved, you’d need to reroute the pipes or install backflow prevention measures to protect the potable water.