Water and sewer design: Simple design with manhole groups

Design with manhole groups is a simplified water and sewer design method.

With this method, all manholes in a group should have the same system point (XY-coordinates for the manhole group are identical). This is maintained with the Move entire group option which is active for simplified water and sewer design.

Figure: P = Presentation point

You use the presentation coordinates of the manholes to distinguish manholes and pipes in the plan presentation.

Mass calculation of ditches is not active for this method. This is because the ditch is built based on the pipes and they must then be designed exactly as described in the next section.

Note

It is the system coordinates that you can export via application layer.

The procedure for the first pipe is the same as with exact 3D design. The difference is that the manhole groups now have the same system point for all data types.

Procedure

Procedure

1. Select the Line definition data... icon on the toolset for Planning, design and execution
2. Select desired SFI model and click OK (you create SFI model as described in the previous section)
3. Create data type for controlling pipe (normally the lowest one)
4. Check CL to indicate that this should be used as line definition
5. Place manholes and bends in the map
6. Edit/supplement with properties directly in the list
7. Generate longitudinal profile optionally with advanced section that is included when the ditch lies in roads or intersections
8. Check/adjust the levels so that requirements for gradient and cover are satisfied
9. Add remaining data types
10. Copy the geometry for the lowest pipe, adjust the levels and edit/supplement with properties
11. Switch to plan view and edit plan presentation

The first steps (1-8) are identical with exact 3D design and are described in more detail here.

Add remaining data types

When the lowest pipe in the ditch is determined, you can advantageously add the rest of the pipes in the longitudinal profile.

For this you can use Copy and Paste. You can find these by right-clicking in the dialog for water and sewer data. Note that you must create the data types first.

After you have pasted the system points for stormwater into the data type for wastewater, you can adjust the levels. You can find the function for this by clicking on the column header for Level1 and Level2 (Add value...).

Edit plan presentation

When you design water and sewer systems with manhole groups, all system points lie on top of each other in the XY-plane.

You plan system points for all horizontal and vertical bends in the pipe section. These are what you see in the list for line definition data. In addition, all system points also have a presentation point that you can edit dynamically in the screen.

Initially, the system and presentation points are identical. Then you just move the presentation points so that you get all pipes in the ditch visualized. The system points are marked with a small circle with a cross inside when you edit via the properties dialog.

After the water and sewer data has been entered, you can also edit in horizontal and vertical planes with grips (grip handles). Grips are an efficient way to edit geometry for presentation points and labels.

Gradient calculation

When you design with manhole groups, you must remember that it is the system coordinates that determine the gradient of the pipes.

Since the manholes in a manhole group have identical system coordinates, all pipes in the same ditch will also get the same gradient.

The gradient of a pipe is usually specified in per mille ‰.

You calculate the gradient like this:

Gradient = Dh / Length × 1000

Where:

• Dh: height difference between levels
• Length: straight distance from center manhole to center manhole

The distance is not corrected for manhole dimension. This will give you an extra safety factor in the gradient calculation for gravity pipes.