OUR SHOWER CONSTANTLY DRIPS WE HAVE IT TURNED OFF AS FAR AS THE KNOBS WILL TURN.SOMETIMES IT WILL QUIT THEN A BURST OF WATER WILL COME OUT LIKE IT HAS AIR IN LINE THEN IT WILL STEADILY DRIP.THE HOUSE IS 27 YEARS OLD AND WE HAVE CALCIUM BUILDUP.CAN YOU HELP WITH SOME IDEAS TO FIX THE PROBLEM. THANK YOU GLENDA PARKER