Abstract: A surge relief valve comprising a main valve body having a dome port and an inlet port. The inlet port is in fluid communication with a first fluid. The invention further includes a dome reservoir connected to the main valve body via the dome port and arranged to hold a second fluid, and a piston located in the main valve body, the piston in fluid communication with the reservoir, wherein the first fluid exerts an upward force on the piston, the second fluid exerts a downward force on the piston, and the piston is arranged to move in response to a differential in the upward and downward forces, wherein the first and second fluids are isolated from one another.