undrinkable

Undrinkable describes liquids that are not safe or suitable for human consumption. In everyday use it is synonymous with non-potable water and may refer to a water supply, natural water body, or a beverage that should not be consumed.

In water quality and public health, water becomes undrinkable when contaminant levels exceed drinking-water standards or when pathogens are present. Causes include microbial contamination (bacteria, viruses, parasites), chemical toxins (lead, arsenic, pesticides), high salinity, turbidity, and radiological contamination. Natural processes such as groundwater intrusion, contamination from waste, or seawater intrusion can render water undrinkable.

Regulatory bodies establish drinking-water standards that specify acceptable levels for microbiological and chemical parameters. Potability is determined through sampling and laboratory analyses; tests commonly assess indicators such as E. coli and total coliforms, along with pH, hardness, and concentrations of specific contaminants. When water is undrinkable, treatments such as disinfection, filtration, coagulation and flocculation, or desalination are employed, or a safer source is provided.

Besides drinking water, the term also applies to liquids that are unsafe for drinking due to spoilage or adulteration, or to water that is produced for non-potable uses such as irrigation, industrial processes, or toilet flushing.