mechanical connectors 
Pipes joined using nuts and threaded metal parts; a gasket is inserted to tighten them, thus preventing leakage.
Formed by using a nut to tighten a male union nut in a female union nut; leakage is prevented by placing a gasket where the two tubes meet.
Threaded on the outside so it can be inserted into the female union nut.
Flexible washer placed where two tubes meet to prevent leakage.
Part that enables a male union nut to be screwed into a female union nut.
Threaded on the inside so that a male union nut can be screwed into it.