Water derived from wells, drawn from groundwater aquifers, which may be used as drinking water and for food processing in areas without mains supply. Its safety cannot be assumed: wells are vulnerable to nitrate runoff from fertilisers, bacterial contamination from livestock or septic systems, and heavy metals such as arsenic or iron from the surrounding geology. Regular testing for microbes, nitrates, and minerals is essential wherever well water touches food or drink, and treatment by chlorination, filtration, or ultraviolet disinfection is common. In food plants, well water must meet the same potable standards as public supplies, and its variability makes monitoring a permanent HACCP prerequisite rather than a one-time check.