Therefore, the scope of hydraulic works performed in cities is very wide.
An elbow is a pipe fitting installed between two lengths of pipe or tubing to allow a change of direction, usually a 90° or 45° angle, though 22.5° elbows are also made.
It is a fitting which is bent in such a way to produce 90 degree change in the direction of flow in the pipe.It is used to change the direction in piping and is also sometimes called a "quarter bend". A 90 degree elbow attaches readily to plastic, copper, cast iron, steel and lead.
It can also attach to rubber with stainless steel clamps.It is available in many materials like silicone, rubber compounds, galvanized steel, etc.
These elbows can be made from tough nylon material or NPT thread.Źródło: https://en.wikipedia.org/wiki/Piping_and_plumbing_fitting
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