Which term describes a plumbing component that must be emptied by mechanical means?

The term that describes a plumbing component that must be emptied by mechanical means is a sump. A sump is typically a pit or reservoir located below ground level or in a basement that collects water from various sources, such as groundwater or drainage systems. Since sumps are designed to collect water that may be pumped out and are not intended for long-term storage, they require mechanical pumps to remove the liquid when it reaches a certain level.

In the context of plumbing systems, it's essential to recognize that components like grease traps and holding tanks primarily serve different functions. While grease traps help separate grease and solids from wastewater to protect the plumbing systems, they usually require periodic manual cleaning rather than mechanical emptying. Holding tanks, on the other hand, temporarily store waste until it can be disposed of appropriately but are also not defined by the necessity for mechanical emptying as a defining characteristic.