This is because the state of the responsibility of owners of housing blocks and homes can have installations mounted a dozen years earlier.Similar situation may occur also in the case of hospitals.
All such work can be carried out also by plumbers self-employed.
You just have to reckon with the fact that the services contract with an independent plumber probably will prolong the work carried out.
They may rely on both the exchange of a faulty seal and at the connection of the new tap.
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