A PRV valve (Pressure Relief Valve) is a safety device designed to protect pressurized systems, such as hot water geysers, from overpressure. The PRV valve operates by opening and releasing pressure when the system pressure exceeds a preset limit, thus preventing damage to the system.

A multi-PRV valve is a type of PRV valve that has multiple pressure settings, allowing it to handle a range of pressure levels. This is useful for systems that experience varying levels of pressure, as the valve can be set to release pressure at different levels depending on the system's needs.

Multi-PRV valves are typically made of brass or stainless steel and are available in various sizes and pressure ratings. They are commonly used in hot water geysers, HVAC systems, and other pressurized systems to ensure safe and reliable operation.