If you have really hard water, a water softener may be your best option. A water softener is a machine about half the size of a water heater that you hook up to the incoming water source. A water soften adds sodium to your water so you don't want to hook it up to any water source where you drink or cook. If your house does not have the proper plumbing you can hook up the water soften to the cold water inlet on your water heater. Water softeners start at around $250 and go up from there. They also require salt which will cost around $3-$4 per month, depending on how hard you water is.
A water softener works by passing the incoming water through a negatively charged resin. When the water passes through the resin, the positively charged metal ions, that make water hard, combine with the negatively charged ions in the resin making neutrally charged particle. The neutrally charged particles won't leach from the water leaving deposits. The resin is recharged by running a salt brine through it. This salt brine is washed down the drain and can cause problems in the treatment of the sewage. Some municipalities require that the brine mixture be collect and disposed of by a third party.
Since we installed our water soften about 4 years ago, I have really noticed a difference in how well the dish washer and washing machine work. The other benefit has been a major reduction in the amount of limescale and soap scum we have in our showers. If you have hard water, a water soften will save you more then it costs.
