We describe the design of a pilot plant for reducing 200g per day of high-level tritiated water to tritium. It comprises a bed of porous iron pellets surrounding a palladium-alloy permeator to continuously remove hydrogen during the water reaction. Daily regeneration of the reactant pellets using hydrogen produces a volume of waste water equal to the volume of tritiated water reduced in the preceding water reduction step. The contamination of the waste water is reduced by materials selection, and by a little isotope swamping before regeneration