A pressure exchanger includes a rotor, a seal plate, and a seal structure. The rotor is configured to exchange pressure between a first fluid and a second fluid. The seal plate has a first substantially planar seal plate surface and a second substantially planar seal plate surface disposed opposite the first substantially planar seal plate surface. A piston structure extends from the first substantially planar seal plate surface to form a substantially planar piston surface that has a surface area and is substantially parallel to the first substantially planar seal plate surface. The seal plate and the piston structure form a hydraulic chamber routed from a first opening formed by the substantially planar piston surface to a second opening formed by the second substantially planar seal plate surface. The seal structure is configured to couple the second substantially planar seal plate surface to a corresponding surface of the pressure exchanger.