waste pipe vs sewer

waste pipe and sewer both are nouns.

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

As nouns, sewer is a hyponym of waste pipe; that is, sewer is a word with a more specific, narrower meaning than waste pipe:

Other hyponyms of waste pipe include culvert, scupper, cloaca, sewerage, soil pipe, trap.

waste pipe (noun)	sewer (noun)
a pipe through which liquid is carried away	a waste pipe that carries away sewage or surface water
	misfortune resulting in lost effort or money
	someone who sews