Residual pressure describes which of the following in a water supply system?

• A. Residual pressure
• B. Stored potential energy available
• C. Forward velocity pressure at the discharge point
• D. The minimum pressure required in a residential area

Answer: (A)

The main idea here is understanding what residual pressure means in a water supply system. Residual pressure is the pressure that remains in the pipes when water isn’t flowing—essentially the actual hydraulic pressure in the system during non‑flow conditions. It shows how much pressure is left in the network to push water out to outlets when demand picks up again. This differs from stored potential energy, which is about energy available in a storage vessel or elevated tank rather than the instantaneous pressure in the live system; it also differs from forward velocity pressure, which is the dynamic pressure produced by moving water at a discharge point; and it isn’t simply the minimum pressure required in a residential area, which is a design target, not the current pressure in the system. So residual pressure is the remaining pressure in the system when flow is stopped.