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Water Softener - How does it work?

Water Softener - How does it work?

Water Softening Process Hard water enters the water softener system. As it passes through the resin inside the tank, the hard water minerals are attracted to the resin and the water is softened to service the home.

Regeneration Process When the resin becomes saturated with hard water minerals, the water softener system goes automatically into regeneration. This is the process that frees the resin of hard water minerals, making it ready to soften the water again. Brine water is drawn into the tank and rinses the hard water minerals off the resin and down the drain. Once the resin is free of hard water minerals, fresh water rinses the remaining brine water out of the system leaving the system ready for service.


Brine fill – Brine tank is filled to dissolve salt for next regeneration.

Backwash – Flow through the resin bed is reversed. Water flows upward expanding and agitating the resin bed.

Brine in – Brine is educted from the brine tank and passes through the resin bed in a downward flow, thus removing calcium and magnesium that has accumulated on the resin beads and is flush to drain.

Backwash – A second backwash is performed Rinse – The resin is now flushed downward at a set flow rate. This resettles the bed and rinses out any remaining brine left in the resin bed.

Service – Softener goes back into service and ready to soften water.

EXCHANGE CAPACITY DATA 20,000 grain approx. per cu. Ft. 6 lbs. salt-sodium chloride

25,000 grain approx. per cu. Ft. 8 lbs. salt-sodium chloride

30,000 grain approx. per cu. Ft. 15 lbs. salt-sodium chloride Note: To convert parts per million (PPM) or milligrams per liter (mgl) to grains divide by 17.1

Example: Water hardness of 250 PPM (250 PPM divided by 17.1 PPM/gr.) equals 14.6 gr.

It is recommended that a good grade of solar or pellet salt be used.

One-gallon water will dissolve approximately 3.0 lbs. of salt

One gallon of saturated brine weighs 10.74 lbs.

Principles of Softening and Ion-Exchange

Softening of water by the exchange process involves the exchange or substitution of the hardness minerals, chiefly calcium and magnesium, for sodium minerals. The exchange is made possible because the minerals are ionic in nature (often called ionized impurities) which means they have an electrical charge. The ion exchange process is based on the fact that like charges repel one another, and unlike charges attract.

Calcium and magnesium ions in water are actually dissolved rock. They have been dissolved by water, the “universal solvent”, as it trickles down through strata of rock and soil it dissolves calcium and magnesium deposits. This dissolved rock eventually finds its way into an underground aquifer and when water from the aquifer is pumped to the surface, it contains the dissolve hardness minerals of calcium and magnesium and is said to be hard water.

An ion exchange softener exchanges the hardness minerals, calcium, and magnesium, for sodium, from the softener resin. Sodium is less objectionable because it does not build up on surfaces as scale deposits.

All three minerals are positively charged ions called cations. The exchange takes place by passing water containing hardness minerals over a man-made ion exchange resin contained in a suitable tank. The resin, polystyrene divinyl benzene in most modern softeners, consist of millions of tiny plastic beads, all of which contain many negatively charged exchange sites to attract the positive cations. When the resin is in the regenerated state these negatively charged exchange sites hold positively charged sodium cations.

As the calcium and magnesium contact the resin beads in their travel through the resin tank, they displace the sodium ions from the exchange sites. During the ion exchange process, relatively small amounts of other strongly charged cations such as iron and manganese are also removed along with the calcium and magnesium.

Ion exchange is possible for two reasons: (1) All cations do not have the same strength of positive charge and (2) the resin prefers the stronger charged cations calcium and magnesium than it does the weaker sodium cations. The exchanged sodium cations pass downward through the resin “bed” and out the softener outlet, thus, the softener delivers “soft”water.

Eventually, all of the resin exchange sites are occupied by calcium and magnesium and no further exchange can take place. The resin is said to be exhausted and must be regenerated.

The softener resin is regenerated with a dilute brine solution of sodium chloride (common salt) and water. During regeneration the flow of service water from the softener is first stopped. Brine is drawn from the brine tank mixing with a separate stream of water. The brine solution flows through the resin, contacting the resin beads loaded with calcium and magnesium ions. Even though the calcium and magnesium are more strongly charged than the sodium, the concentrated brine solution contains literally billions of weaker charged sodium ions which have the power to displace the smaller number of calcium and magnesium ions. When the calcium and magnesium ions are displaced, the positive sodium ions are attracted to the negative exchange sites is said to be regenerated and ready for the next softening cycle.