Richard
Don’t be quick to assume it is calcium deposits causing your problems. Once, I found coming from an A&O Smith HW heater a white deposit. It turned out to be a new polymer they were using as a protection rod.
Without doing a cheleometric titration (using EDTA and either Erichrome Black T or Calmagite), you cannot be certain it is indeed calcium/magnesium deposits.
I am not a plumber, I am an analytical chemist, and have seen some weird things in water supplies. Good luck. If it is indeed calcium, then a water filter should do the trick. Just ask a LICENSED plumber which one is best for your application.
The Friendly Chemist 
