Operating Pressure is the internal mains pressure that occurs at a particular time and at a particular point in a water supply system.
For gravity systems, maximum operating pressure is the full supply level of the reservoir, less the lowest ground level applicable to the pipeline, plus surge. For pumped systems, maximum operating pressure is the greater of :
- The surge HGL less the ground level, or
- The maximum pump suction HGL plus the no discharge head of the pump, less the lowest ground level.
Minimum operating pressure is due to maximum headloss conditions i.e. minimum supply pressure to the zone combined with peak demand in the zone (maximum water velocity through the pipelines).