Sewer Design: Design Steps

Sewer Design: Design Steps

1 Step 1 - Topographical map

Obtain or develop a map of the contributing area

Add location and level of existing or proposed details such as:

Contours

Physical features (e.g. rivers)

Road layout

Buildings

Sewers and other services

Outfall point (e.g. near lowest point, next to receiving water body)

2 Step 2 - Preliminary horizontal layout

Sketch preliminary system layout (horizontal alignment):

Locate pipes so all potential users can readily connect into the system

Try to locate pipes perpendicular to contours

Try to follow natural drainage patterns

Locate manholes in readily-accessible positions

Step 3- Preliminary sewer sizing

Establish preliminary pipe sizes and gradients

Step 4 - Preliminary vertical layout

Draw preliminary longitudinal profiles (vertical alignment):

Ensure pipes are deep enough so all users can connect into the system

Try to locate pipes parallel to the ground surface

Ensure pipes arrive above outfall level

Avoid pumping if possible

Step 5 - Revise layout

Revise the horizontal and/or vertical alignment to minimise system cost by reducing pipe:

Lengths

Sizes

Depths

Design of certria

The following criteria need to be formulated for design of sewer systems:

Peak rates of dry weather f low (wastewater + groundwater infiltration) heavy producers of wastewater allowance for illicit rain water connections to sanitary sewers design storm runoff coefficient.

Pipe profiles (and materials) Hydraulicfriction constants Minimumslopes of sewers

Outlet levels (maximumwater level, invert for storm water)