This approach can be used to effectively control transients resulting from a pump shutdown or startup. Following a power failure, energy stored in hydraulic or mechanical devices can be converted into kinetic energy to force flow into the system and prevent vapor or air pockets from forming.

Such energy conversions reduce the rate of change of flow and, consequently, the magnitude of the resulting hydraulic transients. Part of the flow enters the surge tank or air chamber at start-up or during the upsurge, thereby reducing the effects of an otherwise rapid increase in flow. Due to its relatively high cost, this very reliable method may not be feasible in small water systems.

The following sections describe specific implementations of the flow-supplement approach.