A rinse-injection box has, between a connection for supplying water from a drinking-water line and an inlet into the rinse-injection box, a valve that opens automatically when water flows in. An opening to the atmosphere prevents water from flowing out of the full box into a drinking-water line that communicates with the connection because the opening prevents the establishment of a vacuum. When the supply of water is discontinued, the valve body will close off the inlet, allowing the vacuum needed for the next rinsing process to become established inside the box. Thus, no non-potable water can be suctioned back into the drinking-water line even when the rinse-injection box is completely full.
