In plumbing there are several types of piping available. Some of the most commonly used piping is:
1) Copper types "M" "L" "K"
2) Steel (Black Iron)
3) Galvanized Steel Piping
4) Pex / Pex AL Pex
With each type of piping comes a different joining method, which we will talk. About here in detail.
With copper piping there are a few main ways to make connections. No matter the size or type the most common is soldering. This is a process where we use a torch to heat up the piping over the melting point of the solder and with the use of acid paste we cause a process called "capillary reaction". This is when the solder is drawn into the joint and seals the two sides together to create a watertight seal. The second way to join copper is called "Compression". There are fittings that are bolted together with what we call a "Ferrule" and it puts pressure against the copper piping to create a water tight seal. There are also rated fittings now that are referred to "Push Fit" Fittings. As homeowners this is the quickest easiest way to do repairs. Basically explained is that the fitting is "Pushed" over top of the copper tubing and a watertight seal is created.
With steel piping there are only two styles of connections available. Galvanized steel piping is the exact same as Black steel piping with the exception that it is zinc coating. The main connection type is threaded. This basically means that it screws together with a "Right Hand" pipe thread. In some older homes and with older cast iron radiators, some were "Left handed" threads. In this case a "Left / Right" was used to draw the appliance closer to the piping or valves.
Pex piping or Pex AL Pex piping mainly has 2 styles of connection. There is a "Flare" type and a "Compression Ring" type. Special tools are used for both types of connections but with different manufacturers come different approved methods. The "Flare" style requires a tool to open the Pex piping with a "Pex Ring" over the connection to be applied directly to the fitting. The other "Compression Ring" style is more widely used as a metal ring is put over top of the piping connecting to a fitting and then "Crimped" with a special tool. The "Push Fit" style of connections work on Pex as well, and in most cases will work from one material to another. So per se if you had Pex installed in your home and wanted to replace it with a copper line, a "Push" style fitting could work in this case.
Although I mention the use of Kitech, the use of this material is virtually banned. There was a manufacturer's defect with the fittings, and in such cases they normally come off the market. Newer homes may have had this installed as the water distribution system, to our knowledge this does not happen anymore. If you think that you have it installed it is best to have a professional Plumber come to inspect the state of your system. The fittings over time have a reaction to water under pressure coming through the lines and causing an "Anti Galvanic" reaction. The minerals were removed from the fittings, therefore causing them to swell and break. There are repair fittings available through the manufacturer if such an instance occurs.