riser main vs piping

riser main and piping both are nouns.

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

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

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

riser main (noun)	piping (noun)
a vertical pipe in a building	playing a pipe or the bagpipes
	a long tube made of metal or plastic that is used to carry water or oil or gas etc.
	a thin strip of covered cord used to edge hems

riser main (adverb)	piping (adverb)
	(used of heat) extremely