water vs water main

water and water main both are nouns.

Word	Noun	Adjective	Verb	Adverb
water	Yes	No	Yes	No
water main	Yes	No	No	No

water (noun)	water main (noun)
a facility that provides a source of water	main (a pipe or conduit) for conveying water
a liquid necessary for the life of most animals and plants
the part of the earth's surface covered with water (such as a river or lake or ocean)
binary compound that occurs at room temperature as a clear colorless odorless tasteless liquid; freezes into ice below 0 degrees centigrade and boils above 100 degrees centigrade; widely used as a solvent
liquid excretory product
once thought to be one of four elements composing the universe (Empedocles), associated with the humour phlegm

water (verb)	water main (verb)
secrete or form water, as tears or saliva
supply with water, as with channels or ditches or streams
fill with tears
provide with water