Which tank is primarily used for waste disposal in an RV?

The black water tank is specifically designed for the disposal of human waste and wastewater from the RV's toilet. This tank collects the sewage and is built to handle the contents safely and in compliance with waste disposal regulations. The construction of this tank is robust to ensure that it can contain the waste without leaking, while often featuring a valve system that allows for controlled discharge at designated waste disposal stations.

In the context of RV systems, other options refer to different types of water storage: the potable water tank is for drinking water, the freshwater tank accumulates clean water for usage in sinks and showers, and the grey water tank is used for wastewater from sinks, showers, and laundry. Each of these tanks has specific functions and capacities, but the black water tank is uniquely designated for the handling of toilet waste, making it the correct answer for the question regarding waste disposal in an RV.