What plumbing term describes the vertical distance between the highest point of the fixture and the flood-level rim?

The term that describes the vertical distance between the highest point of the fixture and the flood-level rim is referred to as "head." In plumbing, head is a term commonly used to express the potential energy in a fluid due to its elevation. This measurement is essential when dealing with drainage and wastewater systems, as it helps determine the adequacy of flow and the ability of systems to handle potential backup situations.

Understanding head is crucial for design considerations in plumbing, particularly in ensuring that fixtures are installed at appropriate heights relative to flood-level rims, which helps prevent overflow and backflow issues. By measuring head, plumbers can also calculate the necessary lift or pressure requirements for pumps and other equipment that manage water flow vertically within a building’s plumbing system.

The other terms mentioned, while relevant in different contexts, do not accurately define this specific measurement in relation to plumbing fixtures. Elevation generally refers to the height of a point in relation to sea level or ground level, static pressure measurements deal with the pressure in a fluid that is not moving, and hydraulic grade relates to the potential energy available to fluid flow, which can encompass various factors beyond just the vertical distance to a flood-level rim. Hence, "head" is the most precise term for this scenario.