Are guest bath does not get used much and the valve in the shower/tub is now almost completely blocked by calcium. Our water heater has been rattling calcium deposits around for quite some time but will not die for the home warranty to replace it. A year or so ago the guest bath valve was "crunchy" and with a few twists of the handle the calcium came undone and it worked just fine. Now we almost have complete blockage and no hot water comes out. Without calling a plumber is there a way to tap n the pipes/valve to get this stuff moving or how can I fix this? Is there a way to introduce CLR to the inside f the system?