(a) The size and slope of a building sewer shall be subject to the approval of the Wastewater Superintendent, but in no event shall the diameter of cast iron or vitrified clay pipe be less than six inches, and in no event shall the diameter of plastic pipe be less than four inches. The grade of the six-inch pipe shall not be less than one-eighth inch per foot. The grade of the four-inch pipe shall not be less than one-eighth inch per foot.
(Ord. 1909. Passed 5-22-78.)
(b) All sewers shall be designed and constructed to give mean velocities, when flowing full, of not less than 2.0 feet per second (0.61m/s), based on Manning's formula using an "n" value of 0.013. The following are the recommended minimum slope(s) which should be provided, however, slopes greater than these numbers are desirable.
Minimum Slope in Feet
Sewer Size per 100 feet (m/100m)
Sewer Size per 100 feet (m/100m)
4 inch (101 mm) 1.00
6 inch (152 mm) 0.60
8 inch (203 mm) 0.40
10 inch (254 mm) 0.28
12 inch (305 mm) 0.22
14 inch (356 mm) 0.17
15 inch (381 mm) 0.15
16 inch (406 mm) 0.14
18 inch (457 mm) 0.12
21 inch (533 mm) 0.10
24 inch (610 mm) 0.08
27 inch (675 mm) 0.067
30 inch (762 mm) 0.058
36 inch (914 mm) 0.046
39 inch (991 mm) 0.041
42 inch (1,067 mm) 0.037
(Ord. 2717. Passed 5-14-01.)