clog up vs congest

clog up and congest both are verbs.

Word	Noun	Adjective	Verb	Adverb
clog up	No	No	Yes	No
congest	No	No	Yes	No

As verbs, clog up and congest are synonyms defined as:

Other synonyms of clog up include back up, choke, choke off, clog, crap up, foul.

clog up (verb)	congest (verb)
become or cause to become obstructed	become or cause to become obstructed