Why are floor drains connected to the sanitary sewer system?

Floor drains are connected to the sanitary sewer system primarily because they collect wastewater that is often contaminated. These drains are designed to handle water that may include pollutants from areas such as kitchens, bathrooms, or industrial settings. When a floor drain captures water, it is essential that this potentially hazardous waste is transported away from the building to a treatment facility, where it can be properly managed.

The connection to the sanitary sewer ensures that any waste material, including organic matter, grease, or chemicals, is treated according to local regulations and standards. This helps to maintain public health and environmental safety by preventing contaminants from entering the groundwater or surface water systems.

The other options do not accurately describe the primary function of floor drains in relation to the sanitary sewer system. For instance, while enhancing drainage speed may be an advantage of good design, it's not the primary reason for the connection to the sewer. Similarly, the suggestion that floor drains usually collect clean water contradicts the purpose of connecting them to the sanitary sewer, which is meant to address contaminated waste. Lastly, while preventing backflow issues is critical in plumbing design, it does not specifically relate to why floor drains are connected to the sanitary sewer system.