When to use it?
Some people use it when there is a small leakage/broken pipe.
For me, i use it at the location where i need to replace the section of the pipe/device periodically for maintenance.
E.g,. At the Irrigation Water Timer (Before & After).
How to use it?
Provide both ends of the pipes with male connector. Screw the female part of Union Connector tightly to the male connector; same steps for both sides. Use Teflon tape to provide seal to the threaded area.
For full video, click here.
P/s: There are also some other type of fittings/connectors that can do exactly the function, such as PVC Compression Connector which uses Slip-On instead of Screwing Method. Personally, i prefer screwing type. They are stronger and more reliable in my opinion.