riser main vs pipage

riser main and pipage both are nouns.

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

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

riser main: a vertical pipe in a building
pipage: 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 pipe, piping.

riser main (noun)	pipage (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 fee charged for the use of pipes