Valves and Valve Equipment

Pressure Sustaining Control Valve: The Hydraulic Valve That Protects Inlet Pressure

Learn how pressure sustaining control valves hold upstream pressure at a set minimum, their role in pump and filter lines, and how to install and set them.

ORFA Technical TeamUpdated: Oct 30, 20264 min read

Hydraulic pressure sustaining control valve

In pumping stations, filtration units, irrigation networks and sloping water lines, the pressure at a certain point must not fall below a minimum for the system to work correctly. A pressure sustaining control valve holds the pressure on its inlet side at the set value: while the inlet pressure is above that value it passes water downstream, and when it starts to fall toward the set point the valve throttles or closes to sustain the upstream pressure.

This article explains the operating principle, the problems the valve solves, its applications and the steps for installation and setting.

What Is a Pressure Sustaining Control Valve?

It is a pilot-operated hydraulic control valve made up of a main valve and a pressure sustaining pilot. It works on line pressure and needs no external energy. Unlike a pressure reducing valve, it controls the inlet (upstream) pressure rather than the outlet pressure.

How Does It Work?

Inlet pressure above the set point: The pilot allows the main valve to open and water passes downstream.
Inlet pressure falling toward the set point: The pilot throttles the main valve so the upstream pressure is maintained.
Inlet pressure below the set point or no flow: The valve closes and stays drip-tight.

As a result, however much downstream demand increases, the upstream pressure cannot drop below the defined minimum.

Advantages

Constant inlet pressure: Keeps upstream pressure at the set value regardless of flow changes.
No energy required: Operates on line pressure.
Pressure zoning: Prevents pressure in higher zones from collapsing due to demand in lower zones.
Controlled line filling: Allows an empty line to be filled in a controlled way, preventing sudden discharge and excessive flow at the pump outlet.
Pump protection: At a pump outlet the valve stays closed until the pump builds pressure, helping the pump start under low load and preventing it from running off its curve into an empty line.
Filter backwashing: Installed downstream of a filter, it maintains the minimum pressure needed for backwashing.
Flexible installation: Can be installed in horizontal or vertical lines.

Applications

Pumping stations: Keeping a minimum pressure at the pump outlet so the pump and system stay in a safe operating range.
Filtration systems: Providing sufficient flushing pressure in automatic backwash filters.
Water distribution networks: Protecting the pressure of a priority zone between zones at different elevations.
Irrigation systems: Sustaining head-end pressure to help distribute water evenly.
Industrial processes: Applications that require a minimum line pressure.

Valve type	Pressure controlled	Typical task
Pressure reducing	Outlet (downstream)	Lower high pressure to the required value
Pressure sustaining	Inlet (upstream)	Keep upstream pressure at a minimum
Pressure relief	Line pressure	Discharge excess pressure from the line

Installation and Setting

Installation

Install the valve in a horizontal or vertical line following the flow arrow.
A strainer upstream of the valve is recommended.
A pressure gauge on the valve inlet is needed for setting.

Pressure Setting

Pressurise the system and read the inlet gauge.
If the reading is below the required pressure, turn the pilot adjusting screw clockwise to raise the set point.
If it is above the required pressure, turn the screw anticlockwise to lower the set point.
When finished, lock the adjusting screw with the lock nut.

Tip: If both pressure sustaining and pressure reducing are needed at the same point, a combined pressure sustaining and reducing control valve can be a more compact solution.

Frequently Asked Questions

What is the difference between a pressure sustaining valve and a pressure reducing valve?

A pressure reducing valve controls the outlet pressure and lowers it to the set value. A pressure sustaining valve controls the inlet pressure and prevents it from falling below the set value.

Does a pressure sustaining valve discharge water to atmosphere?

Not when installed in-line; it passes water into the downstream line. Removing excess pressure by discharging water to atmosphere or a tank is the job of a pressure relief valve.

Why use a pressure sustaining valve at a pump outlet?

The valve stays closed until the pump develops enough pressure, so the pump starts under low load, empty lines fill in a controlled way and the pump stays in its safe operating range.

Conclusion

A pressure sustaining control valve secures upstream pressure in pump, filter and distribution lines, keeping the system stable and efficient. Placing it at the right point and setting the pilot carefully protects equipment and prevents operating problems. You can explore other pilot-operated valves in our hydraulic control valves product group.

Online Store