Most people just want their water conditioning equipment to work, and they don't care how.  But if you're one of those curious types, here is the short version of how a water softener does its thing.

  Water is considered to be 'hard' when there is an over abundance of calcium and magnesium in it.  The symbols for these two minerals are Ca and Mg.  When it rains, the water that falls is naturally soft, but the rock and soil in your area may be filled with hardness minerals.  As the water seeps through, it picks up these minerals, turning it into 'hard' water.  It is the water softeners job to remove these minerals.

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In order to do this, your softener must replace the calcium and magnesium ions in the water with sodium ions.  Inside of your softener tank there is a media bed which is made up of many thousands of little round plastic beads.  As the water flows through the media bed, the sodium ions swap places with the calcium and magnesium ions.  After awhile, the sodium ions are exhausted and only calcium and magnesium ions remain, at which point it stops softening the water.  It's time to regenerate.

When you add salt to your tank, it dissolves in the small amount of water in the bottom.  This is called brine.  During regeneration, the softener brings the brine water into the main tank and spends some time flushing it through the media bed.  The sodium chloride (salt) reacts with the beads causing them to displace all of the calcium and magnesium ions, replacing them with sodium ions.  The brine solution, calcium, and magnesium are then rinsed away down a drain, and the whole process is started again.

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Regeneration takes about 90 minutes, and each step in the process is very important.  Not regenerating long enough will keep the media bed from swapping ions completely, and you may end up with hard water before the next regeneration.  Not rinsing long enough can make your water taste salty.  This is why most water softeners are programmed to regenerate in the middle of the night when it is less likely to interfere with normal water usage.

So there you are, now you know how a water softener works!