My wife and I are fans of seltzer but drinking the cans at home seems like a waste.  I have found filling a keg with 5 gallons of tap water and adding a campden tablet plus 2-5 cups of juice for flavor makes a nice mildly favored seltzer.  I put the kegs on 25psi of pressure for carbonation.  Unless it gets kicked out for beer there is always some cold and cheap seltzer on tap.