What causes hard water to form scale deposits?

When scale forms, it forms because of calcium carbonate precipitating out of solution. When hard water is heated, the calcium carbonate can no longer stay dissolved and precipitates - or falls out of the water – as scale. How come I do not see scale on my faucets when the water company tells me I have hard water? Just having hard water doesn't mean you will have scale or even see the effects of the hardwater. Your waters pH level will make a big different as to whether you see any scale or not. If your pH is below 7.0 you will see little to no scale. If your pH is above 7.0, which most city water will be, you will see scaling from the hardness in your water. Why do people get a softener if they see no scale and just need a filter? Carbon filters will raise the pH of your water. As a result, the increase in your pH in some cases is enough to cause scale build up you didn't have before. As such, pairing a whole house filter to a whole house softener is often the best measure to keep ...  more