How often and what kind of inspection or maintenance of sewer pipes are performed?

As for the main line and the quasi-main line (those with a pipe diameter that can be inserted by humans), a large amount of sewage flows at all times, so it is difficult to generate sediment such as sludge, but places where it is easy to accumulate due to the structure and laying The old and aging sewer pipes in the year are surveyed and inspected sequentially and repaired depending on the situation.

Branch lines (those with a pipe diameter that cannot be accessed by humans) have little water flow and easy to stay, so we regularly clean and inspect to maintain the flow function and repair abnormal areas.