A method of obtaining usable water comprises supplying water-bearing vegetable matter 16 to a chamber 12, drawing gas from the chamber to reduce the pressure in the chamber, applying heat to the vegetable matter, causing water to evaporate from it, condensing water out of the gas drawn from the chamber and collecting the condensed water 32 for use. Preferably the vegetable matter comprises cactus. Ideally the residual vegetable matter is used to generate combustible gas. The method may further comprise capturing waste heat from one or both of: a refrigeration system for supply of a coolant to the condenser and one or more pumps used to draw the gas from the chamber, and supplying at least part of the captured waste heat to the vegetable matter during evaporation of the water. Preferably the method further comprises capturing solar heat and supplying at least part of the captured solar heat to the vegetable matter during evaporation of the water. Also claimed is an apparatus 10 for supply of potable water comprising: a chamber, a vacuum pump 18, a heat source 36, a condenser 20 and a water collection 32 and supply arrangement.
