18-29-608.16.2 High-pressure steam boilers.
   Steam boilers exceeding a pressure of 15 psi (103.4 kPa) and hydronic heating systems designed to exceed a pressure of 15 psi (103.4 kPa) or a temperature of 250°F (121°C) shall not be directly connected to the water supply system. Steam boilers not exceeding a pressure of 15 psi (103.4 kPa) and hydronic heating systems designed not to exceed pressure of 30 psi (306.9 kPa) or a temperature of 250°F (121°C) shall be provided with an in-line pressure-type backflow preventer consisting of two check valves separated by an open air port. The air port shall not be directly connected to the drainage system. The backflow preventer shall be installed in an accessible location on the discharge side of the boiler water supply valve and on the inlet side of the boiler feed valve.