Every water supply pipe servicing a beverage carbonator shall receive its supply through a receiving tank constructed in accordance with Section 18-29-606.5.4 of this Article or shall have installed in the pipe an approved stainless steel in-line-pressure-type backflow preventer consisting of two check valves separated by an open air port conforming to ASSE 1012 or ASSE 1022. The air port shall not be directly connected to the drainage system.