Calculations depend on a variety of parameters that may be configured by you.

Choose Analysis > Calculation Options, Alt+3, or click the Calculation Options button to open the Calculations Options dialog box.

The dialog contains the following controls:

• New: Creates a new calculation option.
• Duplicate: Makes a copy of the selected calculation option.
• Delete: Deletes the selected calculation option. The base calculation option cannot be deleted.
• Rename: Renames the selected calculation option.
• Help: Displays online help for the Calculation Options.

To view the Steady State/EPS Solver properties of the Base Calculation Options

Select Base Calculation Options under Steady State/EPS Solver and double click to open the Properties dialog box.

The following calculation option parameters are available for user configuration:

• Friction Method—Set the global friction method.
• Output Selection Set—Select whether to generate output for All Elements (the default setting) or only the elements contained within the chosen selection set.
• Calculation Type—Select the type of analysis to perform with this calculation options set.
• Consider Pumps and Valves in Min. System Pressure Constraints?— If True the pressures at pumps and valves will be considered.
• Demand Adjustments—Specify whether or not to apply adjustment factors to standard demands.
• Active Demand Adjustments—The collection of demand adjustments that are applied during the analysis.
• Unit Demand Adjustments—Specify whether or not to apply adjustment factors to unit demands.
• Active Unit Demand Adjustments—The collection of unit demand adjustments that are applied during the analysis.
• Roughness Adjustments—Specify whether or not to apply adjustment factors to roughnesses.
• Active Roughness Adjustments—The collection of roughness adjustments that are applied during the analysis.
• Display Status Messages?—If set to true, element status messages will be stored in the output and reported.
• Display Calculation Flags?—If set to true, calculation flags will be stored in the output and reported.
• Display Time Step Convergence Info?—If set to true, convergence/iteration data for each time step will be stored in the output file and displayed in the calculation summary.
• Simulation Start Date—Select the calendar date on which the simulation begins.
• Time Analysis Type—Select whether the analysis is extended period or steady-state.
• Use simple controls during steady state?—When True, simple controls will be active during steady state analyses, else they will not be used. Note that logical controls are never used during steady state analysis.
• Is EPS Snapshot?—If True then an EPS snapshot is run instead of a regular steady state run. An EPS snapshot is a steady state run, but it considers the starting date and time of analysis and applies the appropriate pattern multipliers for that time. Note that since an EPS is not run, attributes such as tank levels are derived from the same initial conditions as a steady state run.
• Equivalent Hydraulic Time Step—In order that the pattern multipliers used in an EPS snapshot run exactly match those in an equivalent EPS run, specify the hydraulic time step of the EPS run that you wish to match.
• Start Time—Select the clock time at which the simulation begins. Duration—Specify the total duration of an extended period simulation.
• Hydraulic Time Step—Select the length of the calculation time step.
• Override Reporting Time Step?—Specify if you want the Reporting Time Step to differ from the Hydraulic Time Step.
• Reporting Time Step—Data will be presented at every reporting time step. The reporting time step should be a multiple of the hydraulic time step.
• Set Water Quality Time Step?—If set to True the Water Quality Time Step can be adjusted, otherwise it is computed by the calcuation engine. It is not recommended that you set this to True.
• Water Quality Time Step—Time interval used to track water quality changes throughout the network. By default, this value is computed by the numerical engine and is equivalent to the smallest travel time through any pipe in the system.
• Engine Compatibility—This field allows you to choose which engine compatibility mode you want to run in. Choose WaterGEMS CONNECT 2.00.12 to get all of the latest engine improvements and fixes made by Bentley and an engine mode that is based upon EPANET 2.00.12. This is the default setting for new models. Choose WaterGEMS 2.00.10 to maintain compatibility with previous version of WaterGEMS CONNECT (V8i SELECTseries 1 and earlier), where the computational engine is based on EPANET 2.00.10. This is the default for upgraded models. If you select one of the EPANET modes, any enhancements, calculation corrections, and bug fixes made by Bentley will be disabled in order to match EPANET version results. Imported EPANET models will default to the appropriate EPANET version.
• Use Linear Interpolation for Multipoint Pumps?—If set to true the engine will use linear interpolation to interpret the pump curve as opposed to quadratic interpolation.
• Convergence Check Frequency—This option sets the number of solution trials that pass during hydraulic balancing before the status of pumps, check valves, flow control valves, and pipes connected to tanks are updated. The default value is 2, meaning that status checks are made every other trial. A value equal to the maximum number of trials would mean that status checks are made only after the system has converged (whenever a status change occurs the trials must continue since the current solution may not be balanced). The frequency of status checks on pressure reducing and pressure sustaining valves is determined by the Damping Factor calculation option.
• Convergence Check Cut Off—This option is the number of solution trials after which periodic status checks on pumps, check valves, flow control valves, and pipes connected to tanks are discontinued. Instead, a status check is made only after convergence is achieved. The default value is 10, meaning that after 10 trials, instead of checking status at every trial indicated by the Convergence Check Frequency setting, status is checked only at convergence.
• Damping Limit—This is the accuracy value at which solution damping and status checks on PRVs and PSVs should begin. Damping limits all flow changes to 60 percent of what the would otherwise be as future trials unfold. The default of 0 indicates that no damping should be used and that status checks on control valves are made at every iteration. Damping might be needed on networks that have trouble converging, in which case a limit of 0.01 is suggested (relative to the default calculation hydraulic accuracy of 0.001).
• Trials—Unitless number that defines the maximum number of iterations to be performed for each hydraulic solution. The default value is 40.
• Accuracy—Unitless number that defines the convergence criteria for the iterative solution of the network hydraulic equations. When the sum of the absolute flow changes between successive iterations in all links is divided by the sum of the absolute flows in all links and is less than the Accuracy, the solution is said to have converged. The default value is 0.001 and the minimum allowed value for Accuracy is 1.0e-5.
• Emitter Exponent—Emitters are devices associated with junctions that model the flow through a nozzle or orifice. In these situations, the demand (i.e., the flow rate through the emitter) varies in proportion to the pressure at the junction raised to some power. The constant of proportionality is termed the discharge coefficient. For nozzles and sprinkler heads the exponent on pressure is 0.5 and the manufacturer usually states the value of the discharge coefficient as the flow rate in gpm through the device at a 1 psi pressure drop.
• Liquid Label—Label that describes the type of liquid used in the simulation.
• Liquid Kinematic Viscosity—Ratio of the liquid's dynamic, or absolute viscosity to its mass density.
• Liquid Specific Gravity—Ratio of the specific weight of the liquid to the specific weight of water at 4 degrees C or 39 degrees F.
• Minimum Possible Pressure—Lowest physically possible pressure. Should be based on vapor pressure of liquid at temperature of interest. Pressure below this value will result in a warning message.
• Use Pressure Dependent Demand?—If set to true the flows at junctions and hydrants will be based on pressure constraints.
• Age Tolerance—If the difference between two parcels of water is equal to or less than the value specified in this field, the parcels are considered to be of equal age.
• Constituent Tolerance—If the difference between two parcels of water is equal to or less than the value specified in this field, the parcels are considered to possess an equal concentration of the associated constituent.
• Trace Tolerance—If the difference between two parcels of water is equal to or less than the value specified in this field, the parcels are considered to be within the same percentile.

To view the Base properties of the Transient Solver Calculation Options

Select Transient Solver Base Calculation Options and double click to open the Properties dialog box.

The following calculation option parameters are available for user configuration:

• Initial Flow Consistency—Flow changes that exceed the specified value are listed in the output log as a location at which water hammer occurs as soon as simulation begins. The default value is 0.02 cfs.
• Initial Head Consistency—Head changes that exceed the specified value are listed in the output log as a location at which water hammer occurs as soon as simulation begins. The default value is 0.1 ft.
• Friction Coefficient Criterion—For pipes whose Darcy-Weisbach friction coefficient exceeds this criterion, an asterisk appears beside the coefficient in the pipe information table in the output log. The default value is 0.02.
• Report History After—Set the time at which reporting begins. The default value is 0.02.
• Show Extreme Heads After—Sets the time to start output of the maximum and minimum heads for a run. You can set these to show beginning at time = 0 (right away), after the first maximum or minimum, or after a specified time delay.
• Transient Friction Method—Select Steady, Quasi-Steady, or Unsteady friction method to be used for transient calculations.
• Generate Standard Output Log?—Toggles the standard output file.
• Show Pocket Opening/Closing—Toggles whether the list of vapor pockets open and close times will be appended to the output text file.
• Generate Detailed Reports?—Toggles the generation of ASCII output text files on or off. These can become voluminous for simulations with many time steps and they are not required for the operation of the FlexTables or graphics. Some users prefer to set this setting to False.
• Report Point History Type—Select All to generate point histories for all points in the text reports, or Only if On Path to generate report Histories only for those points that lie on a path.
• Report Points—Choose the report points type from the following:
  • No Points—No report points are defined.
  • All Points—All nodes in the model are report points.
  • Selected Points—Selecting this option makes the Report Points Collection field active, allowing you to define the report points.
• Report Points Collection—Clicking the ellipsis button in this field opens the Report Points Collection dialog, allowing you to choose the report points from the list of available points, or select them in the drawing.
• Report Times—Choose whether to report Periodically, At Specific Times, At No Times, or At All Times.
• Report Period—Specify the equal intervals of time (default) at which reports are generated. This option is only available when the Report Times property is set to Periodically.
• Report Times Collection—Opens the Report Times Collection dialog, allowing you to specify the times step to be reported. This option is only available when the Report Period property is set to At Specific Times.
• Is User Defined Time Step?—Selects whether the time step is user-defined or automatically estimated.
• Time Step Interval— This option is only available when the Is User Defined Time Step? property is set to True.
• Run Duration Type—Selects whether the run duration is measured in time or time steps.
• Run Duration—Period of time simulated by the model.
• Pressure Wave Speed—Speed for the liquid being conveyed, the pipe material selected and its dimension ratio (DR), bedding, and other factors.
• Vapor Pressure—Pressure below which a liquid changes phase and become a gas (steam for water), at a given temperature and elevation.
• Wave Speed Reduction Factor—The low pressure wave speed reduction factor.
• Decrease Time—The time for the wave speed to decrease from its normal value to the reduced value at vapor pressure.
• Increase Time—The time for the wave speed to increase from its reduced value to the normal value at vapor pressure.
• Generate Animation Data—Set this property to True to generate animation data for selected report paths and points.
• Calculate Transient Force—Set this property to True to calculate transient forces.
• Run Extended CAV—Toggles the standard or extended Combination Air Valve (CAV) sub-model. The vacuum breaker component of CAV admit air into the pipeline during low transient pressures that is subsequently expelled at the outlet orifice(s). The extended model tracks momentum more accurately.
• Flow Tolerance—Flows below this value are assumed to be zero when running the transient calculations. This option is generally used to filter out insignificant flows that could otherwise cause numerical problems during the calculation. See Flow Tolerance for more details.
• Round Pipe Head Values?—Specifies whether pipe head values should be rounded or not. This option is generally used to filer out insignificant differences that could otherwise cause numerical problems during the calculation.
• Initialize Transient Run at Time—If the "Specify Initial Condition" field is set to True, the transient simulation is initialized using results from a steady-state or extended period simulation. Enter a time here to initialize the transient simulation using results from the corresponding EPS time step.
• Specify Initial Conditions?—If set to True, you can manually specify the initial conditions for a transient simulation.

To create a new calculation option

1. Choose Analysis > Calculation Options and the Calculation Options dialog box opens.
2. Choose New.
3. Double-click on the newly created calculation option to open the Calculation Options Properties dialog box.
4. Set the fields for this calculation.
5. Close the properties box.
6. Close the Calculations Options box.