The output reports from a hydraulics calculation program show the flow rates and pressure loss data for each pipe section, and the discharge flow and residual pressure for each sprinkler. The format of this output data varies from program to program, but many programs follow the NFPA format. Key output includes the actual density obtained and the lowest residual pressure occurring for any sprinkler. For most programs, the output information can be based upon a known water supply pressure or it can be based on the minimum supply pressure needed to meet the system demand pressure. These two output modes are typically referred to as supply and demand based output.
Supply based output reflects the system operation given a certain water supply pressure.
Demand based output shows how the system will work when supplied with just enough water pressure to drive all sprinklers at the minimum allowed residual pressure. One other report often produced by hydraulic calculation programs is a water supply and demand graph. If two flow and pressure conditions are known for the water supply, then a straight line can be plotted on a semi-logarithmic graph that relates available water supply with the system demand requirements of the sprinkler system. If the system demand point is below the water supply line, then the proposed sprinkler system will work with the available water pressure. This graph is an effective way to quickly assess the margin of safety in terms of gpm and pressure there is available to the sprinkler system.