when you open a hydrant and start to draw large quantities of water out of the system, some of the potential energy of still water is converted into the kinetic energy of moving water. However, not all of the potential energy turns into kinetic energy; some of it is used to overcome friction in the pipes.The pressure remaining after this loss is subtracted while the water is flowing is the ________________ . Residual pressure is an important measurement because it _______________. The __________ water that is flowing, the ______________ residual pressure there is. In theory, when the _____________ amount of water is flowing, the residual pressure is _________, and there is no more potential energy to push more water through the system . In the fire service, _____________ is considered the minimum usable residual pressure, as this level reduces the risk of damage to underground water mains or pumps.