Custom Connection represents a connection with user-defined cross section. The flow routing through a Custom Connection.

Parameters to specify:

Length, Slope, either Manning's n or Colebrook-White Roughness, see Connections Inputs.

Upstream (US) Cover Level, Upstream Invert Level, Downstream (DS) Cover Level, Downstream Invert Level and Cross Section.


Height and Diameter/Base Width are displayed but are not editable for a closed Custom. This is because these two values are calculated from the Define Cross Section.

In an open Custom only the Diameter/Base Width is non editable. The Height is calculated based on the upstream Junction's Cover Level and Invert Level, if the Cross Section's max Height is bigger then the Junctions CL-IL then this Height is used instead. If the Connections Height, USCL or USIL is user defined these values are used instead.


Automatic Setting of Levels

Where possible connection levels are automatically set from Surface Data data, existing Stormwater Controls - SWC and existing Junctions. This is done following the rules below but can be overruled by the user. Where levels have been overruled by the user or by the Pipe Sizing procedure the values will be shown in red to indicate they are no longer following the rules below and will not be automatically updated.

US Cover Level

  • If the US coordinate is on a surface then set the US Cover Level to be the surface level at the US coordinate (in the case of a Stormwater Control this may be at the location of an Inlet or Outlet).
  • If the US coordinate is not on a surface (either a surface is not loaded or the US coordinate is not on a surface) then set the US Cover Level to the Cover Level of the upstream Manhole or the Exceedence Level of the upstream Stormwater Control.

DS Cover Level

  • If the DS coordinate is on a surface then set the DS Cover Level to be the surface level value at the DS coordinate (in the case of a Stormwater Control this may be at the location of an Inlet or Outlet).
  • If the DS coordinate is not on a surface (either a surface is not loaded or the DS coordinate is not on a surface) then set the DSCL to the Cover Level to the Cover Level of the downstream Manhole or the Exceedence Level of the downstream Stormwater Control.