drainage well vs drain system

drainage well and drain system both are nouns.

Word	Noun	Adjective	Verb	Adverb
drainage well	Yes	No	No	No
drain system	Yes	No	No	No

As nouns, drainage well and drain system are synonyms defined as:

drainage well and drain system: a system of watercourses or drains for carrying off excess water

Other synonyms of drainage well include storm drain, storm sewer, stormwater drain.

drainage well (noun)	drain system (noun)
a system of watercourses or drains for carrying off excess water	a system of watercourses or drains for carrying off excess water