It is important, however, that even the smallest failure to call the appropriate professionals, because even if something on the surface it seems to us trivial, inadequately repaired, can result in a much higher failure and pretty large problems.
Repair small defects do not pay much, and good specialist will deal with it quickly and professionally.It is so much simpler, cheaper and better solution than self-repair.
A union is similar to a coupling, except it is designed to allow quick and convenient disconnection of pipes for maintenance or fixture replacement.
While a coupling would require either solvent welding, soldering or being able to rotate with all the pipes adjacent as with a threaded coupling, a union provides a simple transition, allowing easy connection or disconnection at any future time.
A standard union pipe is made in three parts consisting of a nut, a female end, and a male end.
When two dissimilar metals are in contact with an electrically conductive solution (even tap water is conductive), they will form a battery and generate a voltage by electrolysis.When the two metals are in direct contact with each other, the electric current from one metal to the other will cause a movement of ions from one to the other, dissolving one metal and depositing it on the other.
A dielectric union breaks the electric current path with a plastic liner between two halves of the union, thus limiting galvanic corrosion. Rotary unions are unions that allow for rotation of one of the united parts.Źródło: https://en.wikipedia.org/wiki/Piping_and_plumbing_fitting.