AFT Fathom works almost exclusively with the concept of the loss factor, also known as K factor or resistance factor. In some Properties Windows, other popular methods for specifying loss information are provided where they are consistent with the loss factor method. For example, you will find Cd (discharge coefficients) for orifices.

AFT Fathom has methods available for modeling irrecoverable losses with the equivalent length method with either user defined equivalent lengths (input as an Additional Equivalent Length) or NFPA 13 table data (which is the table on the Fittings & Losses tab on the Pipe Properties window). In order for the fittings and losses to be modeled as equivalent lengths, the Include Equivalent Lengths option on the Junction Loss Models panel in Analysis Setup must be checked. Refer to the NFPA panel topic for more information on generating an NFPA Output Report.