Appurtenances are devices that facilitate and control the flow of wastewater and allow access for maintenance activities. They include manholes, building connections, junction chambers or boxes, and terminal cleanouts, among others. Regulations for using appurtenances in sewer systems are well documented in municipal design standards and/or public facility manuals. Manholes for small sewers 24 inches in diameter or less are typically 4 feet in diameter. Larger sewers require larger manhole bases, but the 4 foot barrel may still be used.
Manhole spacing depends on regulations established by the local municipality. Manholes are typically required when there is a change of sewer direction. However, certain minimum standards are typically required to ensure access to the sewer for maintenance. Typical manhole spacing ranges between 300 to 600 feet depending on the size of the sewer and available sewer cleaning equipment. For example, one municipality requires that the maximum manhole spacing be at intervals not to exceed 400 feet on all sewers 15 inches or less, and not exceeding 500 feet on all sewers larger than 15 inches in diameter.
Manholes are installed in the following places:
Manholes are used to place persons, equipment and materials in these sewers for inspection, maintenance and solids removal from cleaning operations. Manholes, on straight runs, should be spaced between 300 and 600 ft. Manholes are also placed at changes in:
* Pipe size
Calculate the height of water standing in a manhole
What is the height of wastewater in a manhole if there is 350 gallons in it? The manhole has a radius of 4 ft.
The manhole is a cylinder. To find out the height of the water solve for the height in the volume of a cylinder equation. Convert the radius into the diameter.
Height = (350 gal) / (7.48 gal/cuft) = 46.79 ft3
(Volume) / (0.785 X D X D) = (46.79 ft3) / (0.785 X 8 ft X 8 ft) = 0.93 ft OR
(Volume) / (3.14 X R X R) = (46.79 ft3) / (3.14 X 4 ft X 4 ft) = 0.93 ft