Nomenclature

The following procedure is recommended for the nomenclature of manholes and sewers.

(a)        First distinct number such as 1, 2, 3 etc., is allotted to the manholes of the trunk sewers commencing from the lower end (outfall end) of the line and finishing at the top end.

(b)       Manholes on the mains or sub-mains are again designated as numbers 1, 2, 3, etc., prefixing the number of the manhole on trunk/main sewer where they join. Similar procedure is adopted for the branches to branch main.

(c)        If two branches, one on each side meeting the main sewer or the branch sewer, letter 'L' (to represent left) or letter 'R' (to represent right) is prefixed to the numbering system, depending on the direction of flow.

(d)       If there is more than one sewer either from the left or right, they are suitably designated as L1, L2, L3, or R1, R2, R3, the subscripts refer to the line near to the sewer taking away the discharge from the manhole.

For example, in Figure 1, L2 R 3.1.2 represents the second manhole on sub-main (L2) through which flow reaches manhole 3.1 of the main sewer, located right side of the manhole number 3 of the trunk sewer. The first numeral (from the left) is the number of the manhole on the trunk sewer. The numerals on the right of this numeral, in order, represent the manhole numbers in the main, sub-main etc., respectively. The first letter immediately preceding the number denotes the main and that it is to the right of the trunk sewer. Letter to the left in their order represent sub-main, branch respectively. The same nomenclature is used for representing the section e.g. Section, L2 R 3.2.2 identifies the section between the manhole L2 R 3.2.2 and the adjoining downstream manhole.

                                            Figure 1: Nomenclature of Sewers