Pressure reducing valves are commonly known as PRVs. They sometimes share this acronym with pressure relief or release valves, but it is important to differentiate between the two. For clarity, the latter are frequently labelled SRVs (safety release valves) or PSVs (pressure safety valves). In this guide, PRV means pressure reducing valve.
A pressure reducing valve is used for lowering and regulating water or air pressure between the upstream (inlet) and downstream (outlet) sides. We will discuss their workings in more detail a little later. In summary though, for a typical water installation:
- A PRV will sit in-line on a mains inlet pipe
- It allows the user to adjust the desired outlet/downstream pressure, usually via a dial or wheel on top of the valve
- Once dialled in, the PRV will continually open and close slightly in response to upstream pressure and flow rate
- Its job is to maintain a safe and consistent pressure on the downstream side, under both flow and no-flow conditions, following the parameters set by the user
By contrast, a pressure relief valve refers to a typically automated failsafe device. These are normally designed to offer a path of least resistance in case system pressure rises above a safe maximum, allowing a volume of water/steam to escape suddenly and directly to an outdoor runoff. For sealed plumbing systems, you might see them referred to as blow-off valves. This type of mechanism often needs to be checked and reset after venting.
A pressure reducing valve is instead designed to work continually and incrementally, helping to keep outlet pressure always down to the required level. PRVs feature in many kinds of water installations, including domestic, workplace, industrial and commercial plumbing systems. PRVs are effectively multi-functional - by lowering outlet pressure and flow rate, they also help reduce excessive water consumption and plumbing noise.