Abstract: Filter drum having its surface divided by longitudinal division strips into a plurality of separate filtration sectors each of which is provided with a plurality of lead and trail ports. In each sector, all lead ports communicate with a single manifold through ports in the manifold wall, the manifold is in turn connected to a filter valve by a single conduit; and all trail ports register with ports in another manifold in turn connected by a single conduit to the filter valve. The manifolds are formed as rectangular conduits secured to the inside of the drum wall and extending the full length thereof. The boundaries between adjacent manifolds are located under division strips. The manifold for a given sector is physically located next to the manifold connected to the lead port for the next succeeding adjacent sector. The ports are formed as elongated slots in the drum deck as close as possible and parallel to the division strip.