Taste and odour are interrelated and consumers frequently mistake odours for tastes. In general, taste is most useful in detecting the ionic inorganic constituents of drinking water, whereas smell is most useful in detecting volatile organic constituents. Taste and odour problems constitute the largest category of consumer complaints. Changes in the taste of drinking water may indicate possible contamination of the raw water supply, treatment inadequacies, excessive biological activity due to sediment accumulation, encrustations and/or loss of chlorine residual in the distribution system. There is no accepted method for the quantitative measurement of taste and there is considerable variation among consumers as to which tastes are acceptable.
Water provided for public consumption should have an inoffensive taste. It is desirable that the temperature of drinking water should not exceed 15°C because the palatability of water is enhanced by its coolness. Low water temperatures offer a number of other benefits. A temperature below 15oC will tend to reduce the growth of nuisance organisms and hence minimize associated taste, colour, odour and corrosion problems. In summer and fall, water temperatures may increase in distributed water due to warming of the soil and/or higher temperatures in the source water. Low temperature reduces the rates of decay of chlorine. But it is not necessary to produce water of an acceptable quality.