Where it can work This design can extract water from water-logged soil, or from salt water, but does not need a body of water such as a stream or lake.

Advantages · Produces pure, distilled water from ground water, even if the source is contaminated with inorganic materials such as salt · Pumps water to the surface (through capillary action) and distils it at the same time · Can be made locally with recycled or inexpensive materials · Can be made in any size and shape · Has a low environmental impact · Has no moving parts

Current limitations · The still/pump needs strong sun and temperatures above freezing · The still/pump operates slowly: at the rate of insolation in equatorial countries, and at 50% efficiency, the pump should provide 2-3 litres of distilled water per m2 per day · The evaporating section will need to be cleaned or replaced as mineral salts are deposited there by the evaporating water

Safety precautions · Since the wicking material contains water with impurities and possibly pathogens, the construction method must ensure that the wick material, or contaminants that may fall from the material, cannot come into contact with the condensed fresh water · This design will not purify water that is contaminated with volatile organic compounds, which can evaporate and condense in the fresh water · The materials that come into contact with the fresh water must be non-toxic

What makes the pump work well The evaporating section (the “leaf”) should be as large as possible in proportion to the condensing section. This helps by: · giving the largest possible area for evaporation · causing the highest possible temperature difference between the housing and the surrounding air; the greater this temperature difference, the faster the water will condense on the inside of the housing