The main idea here is gravity drainage and proper elevation relative to where fixtures can be located. The invert of the building drain—the bottom inside surface of the pipe—must be lower than the lowest floor that may contain a fixture. Why this matters: with the drain running below that level, every fixture on any floor above has a clear downward path to the sewer, so waste and water can flow by gravity toward the public or private sewer without needing pumps. This also helps ensure adequate slope and allows cleanouts and venting to function properly, while reducing the chance of backflow creating problems on upper floors, assuming the sewer can accept the flow. If the building drain were not below the lowest possible fixture level, some fixtures could end up with insufficient fall or would require pumping, which complicates design and maintenance. The exact placement also depends on sewer elevation; if the sewer is high enough to accept the flow, gravity drainage can be maintained by keeping the building drain below that lowest fixture level. The other options would not guarantee that consistent gravity flow from all fixtures or proper fall to the sewer, and they don’t address the vertical relationship between the drain and the fixture levels.

Keeping wells far enough apart reduces the chance that contaminants or changes in groundwater flow around one well will affect the other, and it also minimizes interference between the wells’ draw zones. In Wisconsin practice, the minimum separation distance between a water well and a school well is 250 feet, which provides a buffer so surface or subsurface contamination sources near the school aren’t able to impact the other well, and SAMPLEso each well can reliably produce drinking water without shared contamination risks. If wells are closer, overlapping capture zones and faster potential transport paths increase the risk of cross-contamination and variability in water quality.

Total Suspended Solids describe the portion of solids in a water sample that do not dissolve and remain suspended. These particles are large enough to be captured by filtration, and the amount is expressed as mass per volume (usually mg/L). This makes TSS a key indicator of particulate pollution and a measure of how well a wastewater treatment process, like settling or filtration, is removing solids from the water. It’s the standard term because it clearly specifies what is being measured: solids that are suspended, not dissolved. The other phrasings don’t fit the established terminology. Reordering the words changes the conventional name, and phrases like “in sediment” refer to solids that are already settled out or settled matter, not the suspended solids in the water column.

The main idea is that plumbing codes exist to protect people and the environment, not just the look or the structure of a building. Placing and maintaining a plumbing system properly ensures safe drinking water, prevents contamination, and avoids health hazards inside the building. It also covers environmental protection by safeguarding the waters of the state from pollution and backflow-related issues that could contaminate rivers, lakes, or groundwater. That broader scope—protecting the health, safety, and welfare of the public or occupants, and the waters of the state—is why this wording is the best one. The other choices miss either the occupant welfare, the environmental protection, or focus on aspects (like aesthetics or structural integrity) that aren’t the primary aims of the SPS intent.