sewer vs cloaca

sewer and cloaca both are nouns.

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

As nouns, sewer and cloaca are synonyms defined as:

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

Other synonyms of sewer include sewerage.

sewer (noun)	cloaca (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	(zoology) the cavity (in birds, reptiles, amphibians, most fish, and monotremes but not other mammals) at the end of the digestive tract into which the intestinal, genital, and urinary tracts open
someone who sews