How do I stop it from happening

A good water filter and or softener? Does your water leave mineral scale on your fixtures as well? If so you may want a whole house filter/softener, if not you may get by with a filter just for the water heater. There are a couple plumbers on this site that can probably tell you more about what you would need than I can.

Its building on all plumbing

Have a water analysis done to determine the hardness content (dissolved minerals)in your water supply and any other issues that may be related to the water. This can be done by a water treatment lab or reputable water treatment dealer. Hardness minerals will precipitate out of the water when heated causing the problems you have described and leave scale deposits from both hot and cold water. For a certified water treatment professional in your area go to www.wqa.org. Yes it sounds like you need a water softener/conditioner to alleviate this problem. Hard water can quickly destroy appliances and fixtures in the home.
I hope this helps,
RJ