Pressure-Flow Relationships for DistributionSystem Connections

The suggested practice of using single point test data to construct a "straight line" (i.e., hydraulically scaled) water supply plot is investigated herein. It is shown that this widely used practice may lead to large errors in determining the available pressure at a connection for a design flow condition. It is further shown that using a second test point to construct a quadratic water supply plot can produce far better accuracy. Inaccurate plots of the available pressures can lead to erroneous fire flow predictions and improperly designed fire protection sprinkler systems. This raises safety concerns in addition to poorly designed facilities.