Pipe Installations
Waste Line Slope
All sewage or waste lines should have a downward slope 
of 1/8 to 1/4 inch per foot for their entire run. There should be no low spots, sags or slopes of more than 1/4 inch per foot. Low spots or sags tend to allow sewage to accumulate and create vulnerabilities for leaking and blockage.
Water supply and waste lines should be supported every 4 feet. This support can be in the form of brackets, wire hangers, or in some cases, the pipes run through structural members such as joists. The brackets should be the same or a material compatible with the piping. If this is not possible, there should be a separation between the dissimilar materials.
