For lack of a water supply system, the citizens would be reluctant to sink their own well, gather rainwater, and treat it cautiously. In old times Italy was highly developed, famous for its complex aqueducts that channeled water through municipal streets, delivering it to buildings.
In today's world people use municipalities that pump water from various sources like lakes, rivers, and reservoirs and then filter and treat it so that it can be used for consumption. Some of the water supply comes from rainwater and is collected in the form of snow pack. Intricate piping and canals running hundreds of miles from higher elevations deliver water to treatment centers.  In some countries well water or ground water is also a source of water and is tapped and pumped up to the surface.
Before water is publicly distributed, water is filtered several times before it is treated with chlorine, ultraviolet light, and other chemicals that kill harmful bacteria and microorganisms. Some communities treat the water with iodine and fluoride. After the purification process the water is delivered to storage facilities such as water towers where it is kept and monitored to meet the demands of the public.
Domestic water supply or system (DWS) is a comprehensive term for the potable water supply systems in residential, commercial, institutional, and industrial buildings. Potable water is drinking water, but is used in more quantities for operating plumbing fixtures that are not intended for drinking or cooking.
Portable water supply may come from several sources:
• municipal water supply
• water wells
• delivered by truck
• processed water from creeks, streams, rivers, lakes, rainwater, etc.
There are two basic components the domestic water system consists of:
- The Inlet, potable water side, internal distribution system with plumbing/piping/heating
- The Outlet, sewage/waste water side removal and collection system.
Domestic water systems were in demand from times immemorial, when the first rational man located his dwelling-place nearby the river, stream, etc., with the purpose of fresh running water presence and removing waste water from the home.
Modern indoor plumbing provides each service point in the distribution system with clean, safe, potable water. Clean water must not be contaminated by the waste water (disposal) side of the process system.
The water supply of the most modern western water systems is a direct feed from a municipal water system by a high-pressure pipe, usually located under the road or street. In order to allow the supplier to charge appropriately for the water usage a water meter is installed. Many houses in rural areas still use a cistern or a well where convenient water supply is not available; a pump and pressure tanks are used to create and maintain system pressure needed for operating the plumbing fixtures.
It is in order of things when external water supply provides cold, unheated or cooled water. The cold water supply system possibly will comprise water softener or filter appliances. In that case this cold water is delivered to required plumbing fixtures. Routinely cold water is intended for outside hose bibbs and water closets (toilets). Nevertheless cold drinking water is necessary at lavatories, bathtubs, showers, sinks, dampening apparatus, humidifiers, and freezers as well. In addition, if a building is outfitted properly, water heaters are also use cold water.
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