Water distillers purify water by boiling water and cooling it again. Gases evaporate, bacteria and viruses are killed, and almost every other chemical salt,” mineral and contaminant is left in the boiling chamber.

The condensed water is then passed through an activated carbon filter, which removes organic chemicals which have not been removed in the steam. The distilled water is collected in a storage chamber. The resulting water is extremely pure – comparable to reverse osmosis water.

Distillation units cost between USD600 and USD900. They can be plumbed in under a sink, or can be used on a worktop or table top. Apart from the de-mineralised taste, their other drawbacks include the expense of electricity costs, their low flow-rate, their need for regular cleaning, and their bulk. The resulting water is warm also, so usually needs cooling before drinking. Their major disadvantage for the chemically sensitive, however, is that the water, being de-ionised, absorbs chemicals very readily from its environment and, being usually stored or held initially in a plastic container, has been known to upset people sensitive to plastics. Although it is so pure, in practice chemically sensitive people often tolerate distilled water less well than other types of purified or filtered water.

If you do not want to install a distiller but want to use distilled water, one company The Freshwater Company (address below) supplies distilled water in containers (plastic) in the London and Home Counties area for a cost of between 21p and 25p per litre (2 pints) at 1992 prices. Pharmacies also sell distilled water, usually in plastic containers. You need to check whether it has been distilled with an activated carbon filter distiller. Some distilled or de-mineralised water sold for steam irons or other uses has not been filtered with activated carbon and still contains organic solvents.