Minecraft wiki entry for Item_transportation, associated text: Since water can only flow 7 blocks from the source, it is usually necessary to use multiple water sources. To handle the breaks, a packed ice block and sign can be used. When the items come out of one stream, they will slide across the ice to the next. The sign is necessary to prevent the second stream from flowing backwards. Placing the sign in place of the last water flow block instead of after it eliminates the need for packed ice. You can also use a upright slab allowing the items to pass under the slab.