The hydrator is a module that can be used in the cart assembler. This module when used in a cart, primarily a cart devoted to automatic farming, eliminates the need for water source blocks in farms. The hydrator needs to be filled with water in order for it to work, and it will work similar to water source blocks in that it will water the farm land. Of course, it needs to be refilled with water once it is depleted. A liquid manager can be used to automatically fill the hydrator (This version of the mod is in minecraft 1.5, no FTB mod pack has it at the moment), so it is highly recommended for a liquid manager to be used alongside with a farming designed cart that has a hydrator.