Question

Spacing of manholes in straight sections for diverse pipe sizes is stated in Storm water Drainage Manual. How are figures arrived on?

Answer

For pipe size is less than 300mm, rodding is typically adopted in which workers place about 1m long rods during pipes to location of blockage and physically operate the rod to clear blockage.

For pipe size is less than 700mm, water-jetting is generally working in which water is supplied from nearby fire hydrants and pressurized water jet is used for clearing obstacle.Winching scheme is adopted for every size of pipes.

For example, for pipe size more than 1050mm, it is stated in Storm water Drainage Manual that utmost intervals between manholes length of straight lengths should be 120m. This is as for sizes over 1050m; main method of pipe maintenance is by winching whose utmost length of operation is 120m. Likewise, highest intervals of manholes for other directly pipes are derived from their corresponding protection processes.