It is installed between pipes made from dissimilar metals, and features a female iron pipe thread to solder connection.
It consists of a union nut, two tailpieces, and a gasket that separates the tailpieces to prevent an electric current from occurring.
Installation Notes: Using unions throughout a hydronic installation adds cost to a installation but reduced long term expenses by making replacing, even complex storage tank configurations (as pictured below) easy. When unions are installed on commercial, high out-put applications such as a laundry mat (pictured below) fast replacements are critical. With unions replacing these tanks is easy, we simply isolate the tank with shut off valves, empty tank, disconnect unions and remove and replace tank. Years from now we can replace these tanks in less than 20 minutes.
We prefer the Watts Dielectric Unions for all hydronic heating systems because they are ideal in applications such as hot water storage tanks, water and air conditioners, processing tanks, steam, gas, and water piping. Maximum Pressure: 250psi.