Abstract: The present invention provides a method of and apparatus 1 for water desalination comprising transferring water vapour from salt-water in a vapourization zone 7, via a water vapour transfer zone 12, to a condensation zone 11, and condensing said water vapour into fresh-water. The water vapour transfer zone 12 is maintained substantially free of any gas other than water vapour. Heat is supplied to the vapourization zone 7 and extracted from the condensation zone 11, at relative rates such that there is a net transfer of water from the vapourization zone to the condensation zone. The invention also provides a method of and apparatus for degassing salt water using at least two degassing chambers 17A, 17B each provided with a valved vent 47 and a valved inlet 21,29,90,91, with a valved pipe circuit 17a, 72-82,85-87, having a pump 71.