Do you have a well? Well water often has iron. Iron acts like hardness, but worse—it stains sinks orange and smells like a gym sock.
Add 5 GPG to your hardness number for every 1 mg/L of iron. Seriously. Iron is the diva of the water world. It demands extra attention.
Also, if you have a water filter, softeners play nice with them. But check the manual—mixing systems is like introducing cats to dogs.
