This part of ISO 5667 establishes detailed principles to be applied to the design of sampling programmes, to sampling techniques and to the handling and preservation of samples of drinking water and water used for food and beverage processing (hereafter abbreviated for convenience to drinking water). It includes the processing of water in a treatment plant (including the analysis of the raw water), the supervision of the treatment plant and the distribution system, and the search for defects in the system.This part of ISO 5667 does not include the sampling of sources such as ground water, wells and natural and man-made lakes, the water from which may be used as raw water for a treatment plant. If it is necessary to take samples at these locations, for instance to find a source of contamination of the raw water, sample according to the relevant part of ISO 5667.Sampling is a vital part of the monitoring programme for drinking water. It is important that the sampling purpose be defined as accurately as possible and that the measurements provide the required information in the most efficient and statistically representative manner. It is worthwhile expending appreciable time and effort on the planning and design of sampling programmes; careful planning will normally be well rewarded.Examples of sampling purposes are- determination of the efficiency of the drinking water treatment plant or parts of it (oxidation, disinfection);- quality monitoring of the water leaving the treatment plant;- quality monitoring of the water in the distribution system;- search for the cause of pollution of the distribution system (customer's complaints);- Monitoring of the corrosive potential of drinking water in domestic plumbing;- assessment of the effects of materials in contact with water on the water quality;- monitoring of the influent water and the various processing stages in a food and beverage processing plant, including necessary treatment steps.