About Tap Water
Tap water (running water, city water, municipal water, etc.) is a principal component of "indoor plumbing", which became available in urban areas of the developed world during the last quarter of the 19th Century, and common during the mid-20th Century. The application of technologies involved in providing clean or "potable" water to homes, businesses and public buildings is a major subfield of sanitary engineering.
Waste Water
The waste water from the various appliances, fixtures, and taps is transferred to the waste and sewage removal system via the sewage drain system. This system consists of larger diameter piping, water traps, and is well vented to prevent toxic gases from entering the living space. The plumbing drains and vents article discusses the topic further, and introduces sewage treatment.
Dissolved Gases
Tap watercan sometimes appear cloudy, and this is often mistaken for a mineral impurity in the water. Cloudy water, also known as white water, is actually caused by air bubbles coming out of solution in the water. Because cold water holds more air than warm water, small bubbles will appear in water with a high dissolved oxygen content that is heated or depressurized, because this reduces how much dissolved gas the water can hold. This condition is completely harmless, and the cloudiness of the water disappears quickly as the gas is released from the water.