impure water is re used which reduces the requirement for a supply of replacement impure water making the system 500 suitable for purifying water in locations that do not have a plentiful supply of impure water referring to fig6 and 7 in another preferred embodiment of the invention the evaporation devices 100 may be housed in evaporation modules 600 each module 600 comprises a housing 610 with a window 620 the housing 610 is elongate and can accommodate one or more evaporation devices 100 it is preferably made of an insulating material the window 620 is preferably curved outwardly from the housing 610 this helps to maximise the amount of solar radiation collected by the module 600 the inside surface of the window 620 preferably has a coating that reduces the amount of solar radiation that escapes from the module 600 through the window 620 in use the module 600 may be mounted in a position where it receives a large amount of solar radiation e g on the outside of a building alternatively it may be portable the received solar radiation is collected in the module 600 due to the insulative nature of the housing 610 and the inward reflectiveness of the window 620 e g like an efficient greenhouse heating of the evaporation device s 100 in the module 600 by solar radiation is therefore improved the evaporator 510 of the system 500 illustrated in fig6 may comprise one or more evaporation modules 600 the number of evaporation modules 600 can be varied in the same way as the number of evaporation devices 100 the system 500 may also be.