Tap water is drinking water which comes from an indoor tap or spigot. It is part of a larger indoor plumbing system.
Tap water is potable water supply to a tap valve inside the households or workplace.
The availaility of tap water has major public health benefits, it typically vastly reduces the risk to the public of contracting water borne diseases.
Potable water supply:
Municipal water supply
Water wells
Delivered by truck
Processed water from creeks, rivers, lakes and rainwater

Domestic water systems have been envolving since people first located their home near a running water suppy a stream or river, the water flow also allowed sending waste water away from the domiciles.

Plastic pipe is in wide use for domestic water supply.
Chlorine is a disinfectant which is added to tap water, chorine can leaves organic material like trihalomethanes and haloacetic acids in the water.