Are barrels, lids, cones, and backflow devices all included in manholes?

The correct answer is that barrels, lids, cones, and backflow devices are not all included in manholes.

Manholes are specifically underground structures designed for access to underground utilities, such as sewer systems. They typically consist of the barrel, which is the vertical cylindrical section, and the lid, which covers the opening at the top. Cones may be used as part of the structure to transition from the barrel to the surface, and they can be integral to some manhole designs. However, backflow devices, while they may be related to sewer systems and can sometimes be located near manholes, are not parts of manholes themselves but rather separate apparatus designed to prevent the reverse flow of sewage or stormwater in a system.

This distinction clarifies that while some components of manholes may influence their operation or are in proximity to them, they do not all fall under the definition of what constitutes a manhole structure.