Which action reduces back pressure by removing downstream restrictions?

• A. Increasing upstream water temperature.
• B. Removing downstream restrictions reduces back pressure, potentially allowing a lower discharge pressure to maintain nozzle pressure.
• C. Adding more hoses to the discharge.
• D. Closing the discharge gate.

Answer: (D)

Back pressure comes from resistance downstream of the pump. When downstream restrictions are present, the water can’t flow freely and pressure builds in the discharge line. Removing those downstream restrictions lets water flow more easily, so the pump doesn’t have to push as hard. That means you can lower the discharge pressure while keeping the same nozzle pressure. Closing the discharge gate would do the opposite by increasing downstream restriction and raising back pressure. Increasing upstream water temperature isn’t a reliable way to reduce back pressure, and adding more hoses adds resistance, which increases back pressure rather than reduces it.