What is the effect of a partially closed valve on system pressure?

A partially closed valve restricts the flow of water within a piping system, leading to a pressure differential across the valve. When the valve is partially closed, the area available for water to pass through is reduced, resulting in increased turbulence and friction as the fluid attempts to flow past.

Upstream of the valve, the flow will experience an increase in pressure because water is building up in the section before the restriction. Essentially, the pump or source is still pushing water into that section, creating higher pressure there.

On the other hand, downstream of the valve, the flow is impeded. Since the valve is partially closed, the reduced flow results in a drop in pressure beyond the restriction. As a consequence, the pressure downstream of the valve decreases due to the energy losses from friction and turbulence within the narrowed flow path.

This interaction between upstream and downstream pressures is critical for understanding how valves affect overall system dynamics in irrigation and fluid transport systems. Hence, the correct understanding of this scenario is that a partially closed valve increases the pressure upstream while decreasing it downstream.