Valve definition
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
Employment contracts signed by a plumber
Persons employed as plumbers can sign various contracts of employment. They work full-time in a variety of plants, hydraulic or sign contracts-orders for certain services. Some plumbers also run his own business, under which perform minor plumbing services. Nowadays, self-employed persons often assume hydraulic websites, which include information on the services rendered by them and their price list. They also by posting information about their activities on bulletin boards, and even spread leaflets around the city to encourage use of their services. So they can get regular customers, who will often benefit from their services.
cost estimate repair works carried out in a flooded bathroom
It happens that the household after returning home to find that the bathroom is flooded. In some cases, you can quickly determine the cause of flooding in others but plumbers have to decide to carry out specific work to determine on where the bathroom is leaking water. This will avoid further damage and execution of comprehensive services plumbing. Before plumbers will join the repair work will make them a decent valuation, and sometimes they will have to also prepare for his client the cost estimate, which will allow him to determine whether he will be able to pay for work performed in your bathroom plumbing. Sometimes, however, their performance will simply be necessary regardless of the cost.