The difference between pipes and tubes is simply in the way it is sized.PVC pipe for plumbing applications and galvanized steel pipe for instance, are measured in IPS (iron pipe size).
The temper of the copper, that is whether it is a rigid "joint" or flexible roll, does not affect the sizing.7 The thicknesses of the water pipe and tube walls can vary.
The schedule is largely determined by the operating pressure of the system, with higher pressures commanding greater thickness.Copper tubing is available in four wall thicknesses: type DWV (thinnest wall; only allowed as drain pipe per UPC), type 'M' (thin; typically only allowed as drain pipe by IPC code), type 'L' (thicker, standard duty for water lines and water service), and type 'K' (thickest, typically used underground between the main and the meter). Because piping and tubing are commodities, having a greater wall thickness implies higher initial cost.
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.
When the two ends differ in size, the fitting is called a reducing elbow or reducer elbow. Elbows are categorized based on various design features as below: Long Radius (LR) Elbows ? radius is 1.5 times the pipe diameter Short Radius (SR) Elbows ? radius is 1.0 times the pipe diameter 90 Degree Elbow ? where change in direction required is 90° 60 Degree Elbow ? where change in direction required is 60° 45 Degree Elbow ? where change in direction required is 45° A 90 degree elbow is also called a "90 bend" or "90 ell".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".
It can also attach to rubber with stainless steel clamps.It is available in many materials like silicone, rubber compounds, galvanized steel, etc. The main application of an elbow (90 degree) is to connect hoses to valves, water pressure pumps, and deck drains.
A plumber is a tradesperson who specializes in installing and maintaining systems used for potable (drinking) water, sewage and drainage in plumbing systems.
The term dates from ancient times, and is related to the Latin word for lead, "plumbum".The word "plumber" dates from the Roman Empire.3 The Latin for lead is plumbum.
Roman roofs used lead in conduits and drain pipes4 and some were also covered with lead, lead was also used for piping and for making baths.5 In medieval times anyone who worked with lead was referred to as a plumber as can be seen from an extract of workmen fixing a roof in Westminster Palace and were referred to as plumbers "To Gilbert de Westminster, plumber, working about the roof of the pantry of the little hall, covering it with lead, and about various defects in the roof of the little hall".6 Thus a person with expertise in working with lead was first known as a Plumbarius which was later shortened to plumber.Źródło: https://en.wikipedia.org/wiki/Plumber.