3P Backflow Prevention Valve DN 100 prevents the backflow of any contaminated water entering the rainwater tank. It is suitable for installation in tubes DN 100 and exists of a standard backflow security. The backflow prevention valve allows the water flow only into one direction. A knuckle makes sure that the overflow of the rainwater tank works under normal conditions. If the water flows in the other direction, the valve would close and prevents that dirt is floating into the rainwater tank. The valve has a special sealing integrated.