Can any body explain me the system to construct a backdrop for the sewae system. What should ne the minimum diffrence betweem the depth of the manholes to constuct a Backdrop.

The concept of backdrop manhole is as below;

When there is a branch connection to manhole higher than it's invert level, a backdrop is used in a manhole where the branch is thows the fluid to a manhole in two location. The first, through a pipe drop to the bottom which convey the normal flow. The second, at straight location in the high level which carry sewage only when there is increased flow, Thus limiting splashing occurs to the increased flow and therefore reducing errosion.

The minimum depth should be 6 inches (15 cm)


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