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). Copper tube, CPVC, PeX and other tubing is measured nominally, which is basically an average diameter.
1/2" PVC on the other hand is not the same size as 1/2" tubing, and therefore requires either a threaded male or female adapter to connect them.
When used in agricultural irrigation, the singular form "pipe" is often used as a plural.7 Pipe is available in rigid "joints", which come in various lengths depending on the material.
PeX and CPVC tubing also comes in rigid "joints" or flexible rolls.
Pipe wall thickness is denoted by various schedules or for large bore polyethylene pipe in the UK by the Standard Dimension Ratio (SDR), defined as the ratio of the pipe diameter to its wall thickness.
Pipe wall thickness increases with schedule, and is available in schedules 20, 40, 80, and higher in special cases.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.
This was a source of lead-related health problems in the years before the health hazards of ingesting lead were fully understood; among these were stillbirths and high rates of infant mortality.
Lead water pipes were still widely used in the early 20th century, and remain in many households.
They were often used in Montreal and Boston in the 1800s, and built-up wooden tubes were widely used in the USA during the 20th century.
These pipes, used in place of corrugated iron or reinforced concrete pipes, were made of sections cut from short lengths of wood.Locking of adjacent rings with hardwood dowel pins produced a flexible structure. About 100,000 feet of these wooden pipes were installed during WW2 in drainage culverts, storm sewers and conduits, under highways and at army camps, naval stations, airfields and ordnance plants. Cast iron and ductile iron pipe was long a lower-cost alternative to copper, before the advent of durable plastic materials but special non-conductive fittings must be used where transitions are to be made to other metallic pipes, except for terminal fittings, in order to avoid corrosion owing to electrochemical reactions between dissimilar metals (see galvanic cell).Źródło: https://en.wikipedia.org/wiki/Water_pipe.