clapper valve vs clack valve

clapper valve and clack valve both are nouns.

Word	Noun	Adjective	Verb	Adverb
clapper valve	Yes	No	No	No
clack valve	Yes	No	No	No

As nouns, clapper valve and clack valve are synonyms defined as:

clapper valve and clack valve: a simple valve with a hinge on one side; allows fluid to flow in only one direction

Other synonyms of clapper valve include clack.

clapper valve (noun)	clack valve (noun)
a simple valve with a hinge on one side; allows fluid to flow in only one direction	a simple valve with a hinge on one side; allows fluid to flow in only one direction