How Does a Pressure Reducing Valve Work?

When installed correctly, the Bermad 720 series, pilot operated, pressure reducing valve ensures optimal performance within your pipeline. This article will outline the operation of a pressure reducing valve and the key components that ensure maximum efficiency.

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Function of a pressure reducing valve.

Designed to withstand even the toughest environments, the pressure reducing valve (or PRV) is a hydraulically operated, diaphragm actuated control valve that reduces higher upstream pressure to lower constant downstream pressure—regardless of the fluctuating demand or the varying upstream force. Essentially, the valve maintains a steady state of pressure downstream, heedless of flow.

Watch the function in action:

Key components of a pressure reducing valve:

The pressure reducing valve incorporates a multitude of elements to assist with optimal function.

Valve body.

The valve body works to stabilise the return of flow while regulating pressure.

A look inside the valve body.

The valve body has an internal V port throttling plug that provides an accurate and stable response for flow and pressure regulation while simultaneously reducing noise and vibration. The V port throttling plug also enables the valve to operate close to zero without hunting.

The following animation provides a visual overview of how the V port plug operates with a valve body:

Pilot regulator.

The pilot regulator is responsible for determining the flow of water between the control chamber.

Often referred to as the brain of the valve, the Bermad two-way balanced pilot valve determines the flow of water to and from the control chamber. This coincides with the needle valve to help regulate the flow and maintain a consistent pressure. See our product page to find out more about pilot regulators. 

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Large control filter.

A closer look at the body of a large control filter.

For the valve to work with minimum maintenance and fault-free operation, it’s critical to filter the water entering the pilot regulator.  The larger filter increases reliability of the control valve system and time between maintenance, while minimising faulty operation and maintenance upkeep. To find out more about large control filters, head to our products page.

In the following animation, you’ll see all key components—the body, pilot and filter—working collectively to perform the pressure reducing function.

Watch the full installation, commission and operation of the Bermad 720 pressure reducing valve here:

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Here at Bermad, we’re committed to providing the information you need for products, technology, and operating systems.

If you have any further questions, require additional details or wish to discuss any technical aspects of the pressure reducing valve, you can:

• Contact your local Bermad technical engineer
• View all the present data on the Bermad 720 model
• View our Pressure Relief Valves products page
• Visit our YouTube channel.

If you wish to get hands on experience when it comes to the pressure reducing valve, you can visit the nearest Bermad training facility for an in-person demonstration.

howdy gents!

another reason you're seeing pressure spikes is due to thermal expansion when the system is static and the water heater fires up to heat the cooled off water in the tank that was drawn out. so no water is flowing which means that if you have an incoming pressure of 150 psi then the regulator reduces it to 70 psi, so now when the system is static the the incoming 150 psi overcomes the diaphragm and spring which closes the flow of water and now you have no way for the thermal expansion to relive itself until the 70 psi (low side) reaches 151 psi. the problem is that the temperature & pressure relief vale on the water heater (Tank/tankless) is designed to bleed off pressure when it is too high and then is full open at 150 psi. in my experience prv valves start to bleed off the extra pressure at as low as 125-135 psi. this is why it Byan L is watsing water because the expanding/heated water is causing his prv to leak. this easily solved by installing an appropriately sized thermal expansion tank.

150 psi coming in
regulator lowers it to 70 psi
no water is flowing (Like when your sleeping)
the water heater turns on to heat the cooled off water and the average 40 gallon tank expands approx. 1/2 gallon in volume
the extra volume has nowhere to go and it has a "block wall" stopping it from returning to the high pressure side of 150 psi
this causes the prv to leak.

if you currently do not have a thermal expansion tank. do this:
first thing in the morning when you first turn on the bathroom faucet pay close attention to the flow and you'll notice it starts out very strong and then fades off once the thermal expansion has relieved itself.

Stay thirsty my friends!

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