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About Pipe Network Calculation for Waste Water

Explains the concept of pipe network calculation in waste water.

Detection of Network Geometry and Components

Before calculation, the pipe network is detected with all its details. This is done automatically after clicking Calculate. Only those components are detected whose system types are entered in the Settings dialog.

To analyze the geometry of the pipe network, the section parts are determined first. Section parts in the pipe network will be delimited by T-pieces or by components of dimension changes (e.g. transitions).

The program then searches for the starting component of the pipe network. It can consist of a sewer junction or a partial network end.

On this basis, the flow paths of the pipe network are determined. Flow paths always lead from an initial component to a drainage element, a rainwater feed, a partial network start or termination (exhauster). The number of flow paths in a regular waste water pipe network is thus always equal to the number of installed end components.

Note: When considering initial- and ending components, flow direction of the waste water is not taken into account. This leads to sewer junction or partial network end being considered initial components and drainage elements or partial network start ending components.

Calculation Open Drainage

Prior to calculation you can determine a number of parameters in the Settings dialog, minimum slope for various pipe types or rainfall rate data for example.

Initially, the program determines the waste- and rainwater drain in the network based on the settings for drainage elements and rainwater feed. These depend on the selected building type or on the discharge index, which was either set globally for all section parts in the Settings, or which was assigned individually to the individual section parts.

The thereby determined drains are the basis for the dimensioning of down-, collecting- and ground pipe. Single feed- and collector pipes are always dimensioned according to tables 5 and 9 of DIN EN 12056-2.

If some section parts are without slope information, minimum slope requirements are used for dimensioning. The same happens if a slope is smaller than the minimum slope, the checkbox When the drawn slope too small, insert a minimum slope in the Settings dialog is activated and the Revit-parameter Slope in the Parameter Manager is assigned to the LINEAR parameter LIN_WW_SLOPE in the first place. With this checkbox deactivated, the dimension of the section part is increased until the required hydraulic performance is achieved.

Determining the dimension of a collecting- or ground pipe always leads to a recalculation of the pipe slope. Down-pipes are calculated like a horizontal pipe with minimum slope.

When dimensioning, the filling degree of pipes normally is 0.5 for waste water ground- and collecting pipes and 0.7 for rain- and mixed water collecting pipes. The filling degree can be increased to 0.7 or 1.0 for ground pipes on the outside of buildings. To do this, activate one of the checkboxes Ground pipes behind lifting stations with increased filling level or Ground pipes behind open pit with increased filling level in the Settings dialog. All section parts that have been set to be ground pipes outside of the building will be dimensioned according to DIN EN 12056-2.

Beyond that extend, the program does not create hydraulic certificates or checking for full filling.