waste pipe vs piping

waste pipe and piping both are nouns.

Word	Noun	Adjective	Verb	Adverb
waste pipe	Yes	No	No	No
piping	Yes	No	No	Yes

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

waste pipe: a pipe through which liquid is carried away
piping: a long tube made of metal or plastic that is used to carry water or oil or gas etc.

Other hypernyms of waste pipe include pipage, pipe.

waste pipe (noun)	piping (noun)
a pipe through which liquid is carried away	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

waste pipe (adverb)	piping (adverb)
	(used of heat) extremely