This British Standard gives guidance and recommendations for investigative and planned collection of hot and cold water samples during the life of a building, including sampling locations and the selection of laboratory or on-site testing for those samples. This standard covers sampling from wholesome water systems and water used for make-up where the water is used for immersion or contact, such as spas, swimming pools and therapeutic units. Wholesome water services are systems designed to provide hot and cold water, including water for cooking, drinking and food preparation or washing. Recommendations are given for sampling for the following reasons: one-off sampling for compliance, to evaluate whether the water quality conforms to regulations, guidance, specifications or imposed conditions; ad hoc sampling for verification, to provide assurance that the water being used is suitable for its intended use; sampling for investigation – searching for the cause of concerns or complaints about water quality; random sampling – economically-driven or voluntary sampling used to help confirm or otherwise that water hygiene controls remain effective; and identification and implementation of schemes for commissioning, routine and investigative monitoring of water quality. This standard is not applicable to the sampling of water following outbreaks of Legionnaires’ disease or for the sampling of water from closed systems.