Hard Water contains dissolved minerals in the form of Calcium (Ca), Magnesium (Mg), and Iron (Fe). Removal of these minerals is accomplished by softening the water through an ion exchange process using a water softener. As the water flows through the mineral tank of the water softener, the dissolved minerals become attached to the resin, creating soft water. Over a period of time the resin in the water softener will become exhausted, and the water softener will regenerate using a brine solution produced from the salt in the brine tank. Single Water Softeners with a timed valve , also referred to as "Time Clock Softeners", are programmed to regenerate at a specific time of day. They are usually scheduled to regenerate at 2am, when the demands for soft water are expected to be very low. These can be set to regenerate after a specific number of days, or on certain days of the week.