a rotary union includes a housing which encases a rotor having a first sealing surface and a stator having a second sealing surface . the sealing surfaces are biased against each other due to a load exerted by a biasing member . an inlet chamber is in communication with the fluid being transposed by the union and operates to urge the stator against the rotor due to the pressurized fluid in the chamber reacting against the stator . the stator and the housing define a reaction chamber . pressurized fluid supplied to the reaction chamber operates to urge the stator away from the rotor thus enabling the disengagement of the sealing surfaces .