C.A…….Sand in the toilet bowl may very well be coming in with the water from the city main. This is a very common occurance in my area. When ever there is a break in the city water line, during the course of repair sand very easily enters the line and travels some times great distances befor it is discharged into a private service line. If you are on a private well, I would suspect a failure of a well point or casing. Happy New Year…………..Bud…. Suncoast Plumbing .. Sunny Florida..