Final answer:
Dr. Roy B. Hunter's DFUs measure the discharge into the drainage system and the statement about them being based solely on the smallest or highest load fixture could be false; it's a combination of all fixture contributions. Devices in sink drains aid in optimizing water flow through principles of fluid dynamics.
Step-by-step explanation:
The truth of the statement regarding Dr. Roy B. Hunter's original drainage fixture units can be challenged because it revolves around the specifics of his methodology. Drainage fixture units (DFUs) are a measure of the probable discharge into the drainage system by various types of plumbing fixtures. The concept of the statement implicates the observations of flow rates from plumbing fixtures, where the DFU values are assigned based on the rate of discharge and the frequency of use of various fixtures. It is important to note that the original DFU values consider a range of fixtures, not just the smallest or the one producing the least load, but also those that produce a higher load.
Regarding sink drains, the devices referenced, which might be aerators or certain types of valves or piping designs, work by introducing air into the water flow or by shaping the flow in a way that reduces resistance and turbulence. Such devices optimize the water flow through principles of fluid dynamics, such as continuity and Bernoulli's equation, to speed the flow of water.
In summary, while the concept of fixture units does span the spectrum from small to high-load fixtures, it is not solely based on the extremes; rather, it is a comprehensive analysis of all relevant fixtures and their contributions to the drainage system.