The part of total pressure not used to overcome friction or gravity while forcing water through hose fittings and adapters is known as which pressure?

• A. Residual pressure
• B. Static pressure
• C. Dynamic pressure
• D. Gauge pressure

Answer: (A)

When water is pushed through hose and adapters, the total pressure in the line is partly consumed by losses from friction and elevation as the water moves. The portion that isn’t used to overcome those frictional and gravity losses remains in the system and is available to push water through the remaining fittings and toward the nozzle. That leftover pressure is known as residual pressure—it’s the pressure that remains after accounting for the losses along the path.

For example, if the pump creates 150 psi at the start, and the hose and fittings eat up 50 psi through friction and elevation losses, you’ve got about 100 psi of residual pressure left in the line to drive flow through the rest of the system and establish nozzle pressure.

Static and dynamic (velocity) pressures are related concepts, but this specific phrasing points to the leftover pressure after losses, i.e., residual pressure. Gauge pressure just refers to what a gauge reads relative to ambient, not the distribution of energy after losses.