What is the primary distinction between solid manhole covers and those with holes?

The primary distinction between solid manhole covers and those with holes is related to the type of conveyance they protect and the flow characteristics of the fluids involved. Solid covers are typically used for high-velocity trunk mains, which are designed to carry larger volumes of fluid at higher speeds. In contrast, holed covers are utilized for low-velocity gravity lines, which allow for the gradual flow of fluids without the need for additional pressure.

The design of solid covers provides a more secure and robust seal, preventing debris from entering the system and maintaining the integrity of the infrastructure, especially in high-pressure scenarios. On the other hand, manhole covers with holes are intended to facilitate the entry or exit of gases or liquids, which is crucial for systems that operate under gravity drainage principles. Thus, understanding these distinctions is essential for proper infrastructure management and ensuring the efficient operation of public works systems.