HELLO, MY QUESTION IS CONCERNING MY SIX YEAR OLD WATERHEATER, AND HOW TO CARE FOR THE UNIT TO EXTEND IT'S LIFE. I'M TOLD THAT IT IS NECESSARY TO DRAIN THE TANK TO REMOVE ANY SEDEMENT BUILD-UP FROM THE BOTTOM. WHAT IS THE BEST WAY TO FLUSH AND DRAIN TO MAKE SURE THAT I HAVE ALL OF THIS SEDEMENT OUT ?