Pressure Sustaining Valves (Back Pressure Regulators)

A pressure sustaining valve, also known as a back pressure regulator or back pressure valve, holds the pressure upstream of the valve at a set minimum, regardless of demand downstream. It stays closed until upstream pressure reaches the set point, then opens just enough to pass excess flow while maintaining that pressure.

We supply Z-Tide pressure sustaining valves in direct-acting and pilot-operated designs for liquids, gases and steam, from micro-pressure applications to 12″ pilot-operated valves for high-flow water service.

Our Pressure Sustaining Valves

What does a pressure sustaining valve do?

A pressure sustaining valve protects the part of a system upstream of it. If a large demand opens up downstream, the valve throttles to stop upstream pressure falling below its set point, so upstream processes, equipment or supply zones are never starved of pressure. It is normally closed and opens progressively as upstream pressure rises above the set point.

Pressure sustaining valve vs pressure reducing valve

The two are easily confused because they can look identical. A pressure reducing valve controls downstream pressure: it is normally open and closes as outlet pressure rises. A pressure sustaining valve controls upstream pressure: it is normally closed and opens as inlet pressure rises. Specifying the wrong one means controlling the wrong side of the valve.

Direct-acting or pilot-operated?

Direct-acting valves use a spring working against a piston or diaphragm that senses inlet pressure directly. They are simple, compact and responsive, and suit smaller line sizes and lower flows. Pilot-operated valves use a small pilot to sense upstream pressure and control a larger main valve, giving tighter control across a wide flow range. They are the usual choice for large-bore water systems.

Where pressure sustaining valves are used

Common applications include maintaining priority supply to upstream users or elevated zones when demand surges downstream; holding back pressure on a pump so it doesn't run out on its curve and cavitate, particularly when filling empty pipework; relieving excess flow on a bypass line to protect a pump against dead-heading; maintaining system pressure while filters backwash; balancing pressures in ring mains and parallel pump systems; and holding pressure in vessels and process lines for gases.

How to select a pressure sustaining valve

Start with the set pressure you need to hold and confirm it sits comfortably within the valve's adjustable range. Then consider flow rate and Kv, line size and connection (BSP threaded or PN16 flanged), media and temperature (seal materials for steam or aggressive fluids), and body material. For water distribution at larger sizes, a pilot-operated valve is typically the better fit; for process, gas and smaller lines, a direct-acting valve is usually simpler and more economical.

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