Potable water is water that is fit for human consumption. Without water we die so a safe drinking supply can be deemed essential for life. It should be free of any pathogenic bacteria and parasites. In addition there is usually a legal maximum of chemicals that are allowed in a potable water supply.
The amount of processing required for a water supply to be deemed safe depends on the source water. Water abstracted from a surface source such as rivers, lakes or reservoirs will require extensive processing. Clarification or Flocculation are cemical processes designed to remove a lot of suspended solids. This is usually followed by a filtration step through Granular Activated Charcoal which will remove many organic compounds such as pesticides and any remaining suspended matter. The final step in the production of a potable water supply is a disinfection process usually using chlorine. These processes are continually monitored and water from processing plants must be tested regularly to ensure it meets the statutory requirements for potable water.
Some water sources which derive from protected underground aquifers will require little or no processing to reach potable quality. It is water from such aquifers which is commonly sold as bottled mineral water.
In most of the developed world a safe supply of drinking water is piped directly into the home. Once in the home this water can be used for many different things showers, baths, washing clothes, watering the garden, washing the car, cooking and Oh yes even drinking.
Occasionally there may be an interruption to the water supply either because of a broken main pipe or a power failure at the water works. In these cases when water has to be delivered in tankers rather than by tap it is usually greeted by complaints from the consumer. The luxury of a tanker delivery can only be a dream in much of the developing world where water must be carried manually frequently over great distances and from a contaminated source. The only processing available might be filtering to through a fine gauze sieve to remove suspended matter followed by boiling to kill bacteria and viruses. Often, because of a shortage of fuel for cooking, this is not done. The drinking of contaminated or non-potable water in rural areas of the so called Third World is a major source of preventable illnesses such as cholera and typhoid.
Potable water is a valuable resource that should be available to everyone. Where natural pure water sources are found efforts should be made to protect them from contamination by industrial or human processes. The Victorian sewer system of London was built when it was found that a well supplying drinking water to parts of London had become contaminated with sewage and was the direct cause of a major cholera epidemic.