To calculate the total flow in a water or gas piping system, go to
Ribbon: DM Plumbing->Pipes-> 
Pipe Calculations
Pulldown Menu: DM Plumbing->Pipes->Pipe Calculations
You will be prompted to identify the pipe system for which the total flow is to be calculated.
Select pipe in the system to size:
The total flow in the pipe system will be calculated and stored in the database.
To view the flow value in a specific section of pipe, use the Query Pipe command.