Check the computed headloss in the pipe and make sure it's zero with one decimal place. Basically you would set it so that the head loss (for the initial conditions) for the frictionless pipe would round to zero. Set this to "true", then enter the number of decimal places to round to. In your transient calculation options, you will see a field called "Round Pipe Heads?". In this case, you can use the pipe rounding calculation option. If it still has a positive friction factor listed, then the computed headloss for the initial conditions is probably still slightly greater than zero. Your frictionless pipe should have a zero for the friction factor. You will see a table showing each pipe and the Darcy-Weisbach friction factor that HAMMER used for the simulation (HAMMER always converts pipe head loss to a Darcy Weisbach friction factor for the transient simulation calculations). To ensure that the pipe is indeed frictionless for the transient simulation, you would open the Transient Analysis Output Log (located under Reports > Transient Analysis Reports) after computing the transient simulation, then scroll down to the section beginning with "PIPE INFORMATION". If using the Darcy-Weisbach friction method instead of Hazen-Williams, you would use a very small friction factor. (per the "Headloss" field in the "Results" section of the pipe properties. Product(s): Bentley Hammer Version(s): 08.11.XX.XX, 10.01.XX.XX Area: Layout and Data Input Problem How can I model a frictionless pipe during my transient analysis in HAMMER? Solution To model a frictionless pipe, simply use a very large Hazen-Williams friction coefficient (such as 99,999,999,999), so that the computed headloss during the initial conditions is zero or close to zero. See Also Creating Formula-based User Data Extensions Creating Custom Calculated Results with Formula User Data Extensions - Video 10) Click OK - your custom field will now appear in the model. 9) Use the "alternative" field to choose which alternative your user data extension will be stored in. 8) Use the "Category" field to choose which section of the property grid your field will appear in. When laying out a new element, your user data extension will default to this selection. 7) Click OK and enter an integer value in the "Default value" field, corresponding to the "enumeration value" in the enumeration editor dialog. For example, if your field represents pipe condition, possible "labels" in this list might be "needs repair", "good", etc. Under the "label" column", type the label that will appear in the list. 4) For the "Data Type" field, choose "Enumerated" 5) Click the ellipsis button (.) next to the "Default Value" field 6) In the Enumeration Editor dialog, click the white paper icon to add items to the dropdown list for your field. 3) Type in a name for your field on the left side, or in the "Label" field on the right side. Problem ID#: 48667 Solution 1) Go to Tools > User Data Extensions 2) Right click on the element type you want to add the field to (for example "Pipe") and choose "Add field". Product(s): Bentley WaterGEMS, SewerGEMS, CivilStorm, StormCAD, PondPack, SewerCAD, Hammer, WaterCAD Version(s): 08.11.XX.XX, 10.00.XX.XX Area: Layout and Data Input Problem How can I create a user data extension with more than one dropdown choice? (beyond just true or false) How can I create a custom field for an element, which provides a dropdown list with multiple choices? For example, a "pipe condition" field, with choices like "good", "needs repair", "new".