Back Pressure Maintaining Valves

A back pressure maintaining valve is specifically designed to safeguard the system from going below a set pressure on the inlet side. This type of valve regulates the higher inlet pressure by allowing the seat to open only just as much as necessary to keep the pressure on the inlet side high enough. Back pressure maintaining valves are often used to control pressure within a recirculation loop, relieve excess pressure or to control vacuum.

Where a pressure reducing valve can be considered a “normally open” valve, a back pressure maintaining valve is a “normally closed” valve, it remains closed to ensure that the pressure at the inlet side does not drop below a specific point. These valves still have a set point at which the seat will open to relieve the pressure to avoid over-pressurising the system. However unlike relief valves which perform in a very similar way, these valves are much more reactive and close more readily to ensure that the pressure drop at the inlet is kept to a minimum.

There are two main forms in which back pressure can be regulated:

Spring loaded – these valves rely upon a spring acting down upon a seat / diaphragm. It also utilises the line pressure to assist with the opening or closing of the seat. As the pressure increases the seat begins to close throttling the valve and decreasing the pressure downstream.

Dome loaded – these valves utilise the line pressure to aid with the opening, closing of the seat and the regulating of the pressure at the outlet. This is done by having a diaphragm within a dome structure that has two distinct areas on either side of the diaphragm. On one side of the diaphragm the inlet pressure is fed through a pilot which utilises the line pressure to open the main valve. Once the main valve is open the outlet pressure is fed through to the other side of the diaphragm, this allows the valve to self-regulate ensuring a constant pressure is maintained at the outlet.

PAC maintains strong relationships with industry leaders (like Hale Hamilton) in the air preparation / controls field, which allows us to offer superior products very competitively.

We are not only able to offer a single product, we are able to include our pressure reducing valves as part of an overall unique design solution, tailored specifically for your particular needs. We regularly provide pressure regulating valves to a wide range of industries including Oil & Gas, Defence and Mining.

Our experience and technical knowledge allows you as the customer to have peace of mind that the product offered will be technically sound and of a high quality.


Spring loaded, dome loaded


Stainless steel, brass, bronze, nickel-aluminium-bronze


0 to 241bar

Back Pressure Maintaining Valves Product Range

Dome Loaded
Spring Loaded
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