The need for guidelines to bridge the gap between ideal drinking-water quality and that quality which is practically achievable and acceptable

Classically a distinct boundary is made between ideal and non-ideal water. Such a distinct boundar is not in keeping with resource water quality conditions, especially in a semi-arid climate. To facilitate the decision processes around the supply of quality drinking water, a classification system was devised to give a clearer picture of expected effects on the domestic user. The classification system, which divides water quality into four classes from 0 (ideal) to Ill (unsuitable for use as drinking water without prior treatment), based on the 2nd, 1996 edition, of the South African Water Quality Guidelines for Domestic Use. The classification, however, differs in several respects from the latter: (i) The definition of the user as drinking water for human use, rather than the wider definition for domestic water; (ii) the concept that non-ideal water may be used for short periods only rather than for a lifetime without significant ill effects, as in Class II; and (iii) the emphasis on health effects from drinking-water use, especially in sensitive individuals, such as bottle-fed infants. In the selection of constituents the classification is biased towards those constituents that commonly are of concern in borehole water in rural areas where there is little or no pollution from heavy industry. The present constituent list is not nearly as extensive as that contained in the 2nd edition of the South African Water Quality Guidelines for Domestic Use.