History of water supply and sanitation
Water supply and sanitation has been a primary logistical challenge since the dawn of civilization. Where water resources or infrastructure or sanitation systems are insufficient for the population, people fall prey to disease, dehydration, and in extreme cases, death.
Major human settlements could initially develop only where fresh surface water was plentiful, such as near major rivers. Over the millennia, technology has dramatically increased the distances across which water can be relocated, but the availability of clean and fresh water remains a limiting factor on the size and density of population centers, and is expected to remain so into the foreseeable future.
Źródło: https://en.wikipedia.org/wiki/History_of_water_supply_and_sanitation
The most common plumbing work done in small towns
In the area of small towns they are carried out various plumbing work. They are most often associated with improving water and sewage networks, and above all the wells and the removal of these branches or leaves, and various filth. The implementation of specific services hydraulic ordered also by owners of residential houses, where you need to install new sanitary or check the efficiency of their operations. The homes can also occur failure of hydraulic such as rupture of the seal or hose from the washing machine and the lower belt in a washing machine. Repair any of this type of failure can be reported to the plant hydraulic operating near the town, in which the owners home.
Wikipedia about Valves
A valve is a device that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fittings, but are usually discussed as a separate category. In an open valve, fluid flows in a direction from higher pressure to lower pressure. The word is derived from the Latin valva, the moving part of a door, in turn from volvere, to turn, roll.
The simplest, and very ancient, valve is simply a freely hinged flap which drops to obstruct fluid (gas or liquid) flow in one direction, but is pushed open by flow in the opposite direction. This is called a check valve, as it prevents or "checks" the flow in one direction. Modern control valves may regulate pressure or flow downstream and operate on sophisticated automation systems.
Źródło: https://en.wikipedia.org/wiki/Valve