Abstract: Method of treating hard water containing dissolved and/or suspended volatile non-aqueous material, in which the water is heated by direct contact with steam to precipitate the hardness and resulting in three phases, namely, a gas phase comprising steam and vapor of volatile non-aqueous material, a soft water phase and a sludge (precipitate) phase. The gas phase is separated carrying with it the volatile non-aqueous components derived from the feed water. The soft water phase is separated from the sludge. The separated water phase is free or substantially free of volatile non-aqueous material and is suitable for use in a once through steam generator to produce saturated steam. The steam used to heat and strip the feed water is generated outside the process and preferably is steam generated in a conventional steam generator from a portion of the soft water produced in the process. The remainder of the soft water may be used to generate steam, e.g.