Private interceptor main sewers 6 inches or larger must have a manhole at the most upstream point of the private main, and what spacing and angle requirements?

• A. At every 90-degree change and every 200 feet
• B. Only at the beginning and end of the main
• C. At every branch connection, not more than 100 feet apart
• D. At every 45-degree change in direction and at intervals not more than 400 feet

Answer: (D)

The key idea is ensuring practical access along a private interceptor main for cleaning, inspecting, and maintaining flow. For a 6-inch-or-larger private interceptor main, you start with a manhole at the most upstream point so maintenance crews can reach the line right from the source side. From there, the spacing and angles are set to keep the line testable and cleanable.

Placing manholes at every 45-degree change in direction makes it possible to reach around bends without using overly long or awkward conduits, which helps when rodding or snaking the line. Keeping intervals to no more than 400 feet means a crew can reach any point of the main with standard cleaning equipment, preventing long dead runs where blockages could form or be hard to clear. This combination—manholes at each 45-degree turn and within 400-foot spans—provides reliable access along the entire run.

So the requirement is: a manhole at the most upstream point, at every 45-degree change in direction, and at intervals not more than 400 feet.