(1) Plumbing systems for allowed and permitted floodplain and floodway uses shall conform to the following conditions:

(a) Sewer lines, except those to buried and sealed

vaults, must have check valves installed to prevent sewage backup into permitted structures; and

(b) All toilet stools, sinks, urinals, and drains must be located such that the lowest point of possible water entry is at least 2 feet above the elevation of the base flood.