sewer vs sewerage

sewer and sewerage both are nouns.

Word	Noun	Adjective	Verb	Adverb
sewer	Yes	No	No	No
sewerage	Yes	No	No	No

As nouns, sewer and sewerage are synonyms defined as:

sewer and sewerage: a waste pipe that carries away sewage or surface water

Other synonyms of sewer include cloaca.

sewer (noun)	sewerage (noun)
a waste pipe that carries away sewage or surface water	a waste pipe that carries away sewage or surface water
misfortune resulting in lost effort or money	waste matter carried away in sewers or drains
someone who sews