Yes, Your Washing Machine Is Using Enough Water http://www.consumerreports.org/washing-machines/yes-your-washing-machine-is-using-enough-water/?loginMethod=auto
top load agitator: 25-26 gallons of water
top load impeller (HE): 12-17 gallons
"In many models the laundry is washed in a shallow pool of water. In
some models, the water level is so low you may never even see a pool of
water," says the American Cleaning Institute.
front load: 7 gallon