If you'd like to remove more of the mineral content from your water before it hits the boiler and waterworks, this in-tank, rechargeable water softener will do the trick.

It will work on any machine that has an intake hose down in the water tank, just hook it up to the hose and you're good to go. You can also recharge these -- apparently indefinitely -- by putting it in a glass with a few tablespoons of kosher salt (or any other non-iodized, additive-free salt) and water about once a week.