A piston seal assembly is disclosed comprising a seal and a seal energizer which supports the seal. The piston seal assembly comprises one component that is designed to position the seal energizer in a fixed axial position within the piston groove. In one embodiment, the seal energizer has the shape of a split ring with at least one of its lateral surfaces shaped to position the energizer in a fixed position within a piston groove. In other embodiments the piston seal assembly comprises a spacer that is positioned next to the seal energizer within the piston groove and is designed to position the seal energizer in a fixed axial position. The piston seal assembly can comprise a seal that has a portion which protrudes between the seal energizer and the piston groove wall such that it positions the seal energizer in a fixed axial position within the piston groove.