(1) System design. If a system's configuration will provide substantially equal or greater protection due to the physical laws of gravity and water hydraulics, components of a backflow prevention system may be waived by the department.

(2) Barometric pipe loop.

(a) Barometric loops can only be used on systems pumping from a surface water source.

(b) The barometric pipe loop must be located in the main water line immediately downstream of the irrigation water pump.

(c) A barometric pipe loop must be designed with sufficient elevation differential to compensate for backflow.

(d) The bottom of the barometric loop apex must be at least 30 inches above the highest water-emitting device or of any portion of the irrigation application system.

(e) The barometric loop must contain a vacuum-relief device at the loop apex that allows air into the pipeline immediately upon loss of pressure. The orifice size must comply with current American Society of Agricultural and Biological Engineers (ASABE) standards.

(f) The chemical injection port must be located downstream of, and at least 30 inches below, the bottom of the pipe loop apex.

(3) The department may recognize authorized U.S. Environmental Protection Agency (USEPA) alternative backflow devices, providing they are as restrictive as the provisions of this chapter.