A rotary union includes a housing having a shaft rotatably mounted in a bore. A plurality of annular plates is mounted on the shaft in spaced relation, and a plurality of spools is disposed in alternating fashion between the plurality of annular plates on the shaft. Each spool includes two seal rings creating mechanical face seals with adjacent annular plates. The shaft, the plurality of annular plates and the plurality of spools are arranged to assemble in a stacked arrangement, which is insertable as a whole into the cylindrical bore of the housing.