Grey water in an RV refers to all the wastewater that drains from your shower, kitchen, and bathroom sinks, excluding toilet water. Grey water is generally not as bacteria-filled as black water, which contains human waste and is unsafe. The grey water tank is located underneath the RV and holds wastewater until it can be dumped at an appropriate dump station. Grey water can contain food particles and soap that take time to break down and may attract critters, so it is important to empty the grey water tank at a proper dump station and not on the ground at a campsite. Grey water can be filtered and reused in gardens or lawns if done properly.