riser main vs pipe

riser main and pipe both are nouns.

Word	Noun	Adjective	Verb	Adverb
riser main	Yes	No	No	No
pipe	Yes	No	Yes	No

As nouns, pipe is a hypernym of riser main; that is, pipe is a word with a broader meaning than riser main:

riser main: a vertical pipe in a building
pipe: a long tube made of metal or plastic that is used to carry water or oil or gas etc.

Other hypernyms of riser main include pipage, piping.

riser main (noun)	pipe (noun)
a vertical pipe in a building	a long tube made of metal or plastic that is used to carry water or oil or gas etc.
	a tube with a small bowl at one end; used for smoking tobacco
	the flues and stops on a pipe organ
	a tubular wind instrument
	a hollow cylindrical shape