Abstract: A horizontal filter press (100) is provided with a track (105) and a plurality of filter plate assemblies (101) supported by side bars (104). A washer carriage (2), which is movably supported on the track (105), includes a washer unit (1) for washing the filter plate assemblies (101). The washer unit (1) may include a wash water manifold (11) having a first outlet (13) for feeding wash water to a first spindle (19) and a second outlet (14) for feeding wash water to a second spindle (19). Each of the spindles (19) may include a reel (20) for spooling a flexible hose (23) thereon, and they are each configured to be rotated with respect to the washer carriage (2). A first end of a spray bar (25) fluidly communicates with a first flexible hose (23) supported by a reel (20) on the first spindle (19).