In general terms a private water supply is on which is not a "mains" supply. Most private supplies are situated in the more remote, rural parts of the country. The source of the supply may be a well, borehole, spring, burn, river, loch or lochin. The supply may serve just one property or several properties through a network of pipes. The environmental health department will usually offer to monitor the quality and safety of private drinking water supplies. In most circumstances, for domestic premises this is a free service. Tests on the chemical and microbiological quality of the water will be carried out. Guidance will be provided to improve the quality of the water should it fail any of the tests.