MRV (Back Pressure and Pressure relief valves The “MRV” series back pressure and pressure relief valves help to maintain a set pressure or relieve excess pressure on the pump and system. The 2-port design allows each valve to be used both as a pressure relief and back pressure valve to ensure accurate metering and pump performance. Available in a range of materials, pressure adjustability for 0 to 150 psi, and various connection options, these valves enable installation fit and flexibility for your operations. An optional port enables the use of a standard pressure gauge to see the results of field adjustments.