How do Water Softeners Function?
Almost all water softeners function using a chemical process called ion exchange. The process replaces the calcium and magnesium ions that make water hard with sodium ions. This results in softened water that is safe to use.
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Ion-exchange systems typically use a tank filled with resin beads, which are made from polystyrene and carry a negative charge. When hard water enters the tank, the resin beads attract and cling to the minerals in the water. As the hard water flows through the resin, it exchanges the calcium and magnesium ions for sodium ions.
Once the hard water has passed through the resin beads, it exits the mineral tank and goes into your home’s plumbing system. It will then flow through your appliances and hot water heater.
The salt in the water softener’s brine tank aids the ion exchange process and helps regenerate the resin. A water softener usually requires periodic salt replenishment in order to continue producing softened water.
A typical water softener has three components: a control valve, a mineral tank, and a brine tank. The control valve monitors the water supply and automatically triggers regeneration when it detects a change in the amount of calcium and magnesium ions being exchanged.
A mineral tank is the heart of a water softener. It contains a bed of resin beads or zeolite. These are small polystyrene crystals that carry a negative charge. As the water passes through the resin beads, the calcium and magnesium ions are attracted to the polystyrene crystals.
When these hard water minerals bind to the resin, they release sodium ions to balance their charges. This releases the hard water minerals to allow softened water to be released from the water softener.
Most common water softeners are ion-exchange systems that use polystyrene resin beads and salt. The resin beads carry a negative charge, and when the hard water ions bind to them, they release sodium ions to balance their charge.
These water softeners typically use a counter-current regeneration process, which distributes the sodium ions more evenly around the resin than a co-current type of regeneration. Counter-current regeneration is more effective and saves about 65% water and 75% salt compared to co-current regeneration.
During regeneration, the water softener draws brine solution out of the secondary storage tank and flushes it through the resin in the mineral tank. This process re-exchanges the sodium ions trapped on the resin beads, and the water softener is then cleaned.
A brine tank sits next to the mineral tank and holds a very concentrated salt solution, called brine, ready to be drawn out and used in regeneration. The brine solution is added when the control valve registers that the resin capacity is depleted, and the resin soaks up the salt to restore its positive charge.
The salt in the brine solution also helps keep the mineral tank clean and remove any rust or corrosion that may have built up over time. The salt in the brine solution is a common form of table salt, and it is only ingested in trace amounts that are not likely to be harmful to the health of any person.