A union is similar to a coupling, except it is designed to allow quick and convenient disconnection of pipes for maintenance or fixture replacement.
Pipe unions are essentially a type of flange connector, as discussed further below. In addition to standard, simple unions, other types of union exist: Dielectric unions are unions with dielectric insulation, used to separate dissimilar metals (such as copper and galvanized steel) to avoid the damaging effects of galvanic corrosion.
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.
The major categories of plumbing systems or subsystems are: potable cold and hot tap water supply plumbing drainage venting sewage systems and septic systems with or without hot water heat recycling and graywater recovery and treatment systems Rainwater, surface, and subsurface water drainage fuel gas piping hydronics, i.e.
heating and cooling systems utilizing water to transport thermal energy, as in district heating systems, like for example the New York City steam system.Źródło: https://en.wikipedia.org/wiki/Plumbing
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.