1. Each mobile home stand shall be provided with at least a four-inch diameter sewer riser pipe. The sewer riser pipe shall be so located on each stand as near to the center from front to back as possible and so that the sewer connection to the mobile home drain outlet will approximate a vertical position, as near the center of the stand as possible.
2. The sewer connection shall have a minimum inside diameter of three inches, and the slope thereof shall not be less than one-fourth inch per foot. The sewer connection shall consist of one pipe line only without any branch fittings. All joints shall be air and watertight.
3. All materials used for sewer and sewer connections shall be semi-rigid, corrosive resistant, nonabsorbent and durable. The inner surface shall be smooth.
4. Provision shall be made for plugging the sewer riser pipe when a mobile home does not occupy the lot. Surface drainage shall be diverted away from the riser. The rim of the riser pipe shall extend at least to ground level.