The equipment or piping shall be installed so that it will not provide a cross
connection or interconnection between a distributing supply for drinking or
domestic purposes and a polluted supply such as a drainage system or a soil or
waste pipe that will permit or make possible the backflow of sewage, polluted
water or waste into the water supply system. Where crossing a sewer or waste
lineis inevitable, the water line shall be not less than 0.30 meters above the sewer
line, which shall be cast-iron soil pipe for not less than 30 meters on each side of
the crossing.