Richard
If you are getting that heavy a buildup due to calcium deposits (and probably magnesium deposits as well), you have bigger problems then a clogged bowl, you have VERY hard water. First thing I would do is ask for a water sampling (whic I do, I am an anytlical chemist) and have them test the water with an EDTA-Erichrome Black T titration, and that would tell you the exact extent of the problem. IF that is the case, than you need a water softener. Hopefully your problem has an easier solution that would cost you a lot less.
