A fuel mixing system comprising an integrated housing, including: a mixing assembly configured to mix a liquid fuel and a water to generate a fuel mixture, wherein the fuel mixture is configured to combust in a combustor of a gas turbine, and the mixing assembly comprises: a plurality of liquid passages disposed in the integral housing including a liquid fuel passage configured to flow the liquid fuel, and a water passage configured to flow the water; and a mixer disposed in the integrated housing and coupled to the liquid fuel passage and the water passage, wherein the mixer is configured to mix the liquid fuel and the water to form the fuel mixture; characterized in that: the integrated housing comprises one or more solid metal blocks, and said liquid passages, including the fuel and water passages (70,74), comprise holes or bores in the block or blocks; and in that the plurality of liquid passages, including the liquid fuel passage and the water passage, comprise only downward sloping portions or downward sloping and horizontal portions, such that fuel and/or water is able to drain out of the integrated housing without being trapped within the integrated housing. a mixing assembly configured to mix a liquid fuel and a water to generate a fuel mixture, wherein the fuel mixture is configured to combust in a combustor of a gas turbine, and the mixing assembly comprises: a plurality of liquid passages disposed in the integral housing including a liquid fuel passage configured to flow the liquid fuel, and a water passage configured to flow the water; and a mixer disposed in the integrated housing and coupled to the liquid fuel passage and the water passage, wherein the mixer is configured to mix the liquid fuel and the water to form the fuel mixture; characterized in that: the integrated housing comprises one or more solid metal blocks, and said liquid passages, including the fuel and water passages (70,74), comprise holes or bores in the block or blocks; and in that the plurality of liquid passages, including the liquid fuel passage and the water passage, comprise only downward sloping portions or downward sloping and horizontal portions, such that fuel and/or water is able to drain out of the integrated housing without being trapped within the integrated housing. a plurality of liquid passages disposed in the integral housing including a liquid fuel passage configured to flow the liquid fuel, and a water passage configured to flow the water; and a mixer disposed in the integrated housing and coupled to the liquid fuel passage and the water passage, wherein the mixer is configured to mix the liquid fuel and the water to form the fuel mixture; characterized in that: the integrated housing comprises one or more solid metal blocks, and said liquid passages, including the fuel and water passages (70,74), comprise holes or bores in the block or blocks; and in that the plurality of liquid passages, including the liquid fuel passage and the water passage, comprise only downward sloping portions or downward sloping and horizontal portions, such that fuel and/or water is able to drain out of the integrated housing without being trapped within the integrated housing. the integrated housing comprises one or more solid metal blocks, and said liquid passages, including the fuel and water passages (70,74), comprise holes or bores in the block or blocks; and in that the plurality of liquid passages, including the liquid fuel passage and the water passage, comprise only downward sloping portions or downward sloping and horizontal portions, such that fuel and/or water is able to drain out of the integrated housing without being trapped within the integrated housing.