Photo of a home water softener systemHow Water Water Softeners Work

  • HOW WATER SOFTENERS / CONDITIONERS WORK - CONTENTS: How water softeners & similar water conditioners work, types of water softeners, basics of water softener controls. Comparing Swap-in, Manual, Twin Tank & Automatic Water Softener or Water Conditioner Features. What are the Controls on a Water Softener / Conditioner & What do They Do? What is the Water Softener Recharge or Regeneration Cycle?
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Water softener operation: here we explain how water softeners and similar water conditioners work, types of water softeners, and the basics of what water softener controls are present and what they do. How water softeners work, methods to remove minerals from home water supply.

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How Water Softeners Actually Work - Water Conditioners Operation & Ion Exchange Water Softeners

Water softener equipment (C) D FriedmanConventional ion-exchange water softeners used to remove minerals from "hard" water in buildings usually use salt in an ion-exchange process, swapping in sodium ions (salt) and causing calcium and magnesium to precipitate out of the building water supply (and to collect in the water softener).

[Click to enlarge any image or table]

Definition of "hard water": Hard water is generally taken to mean water containing minerals over 121 mc (micrograms) per liter of water, or over 7 grains of hardness per gallon.

Salt in the brine tank (red arrow in our photo at left) is used to place a charge of salt molecules in the resin tank (green arrow). During a regen cycle (explained below) under control of a timer or on some systems more advanced systems that actually monitor the mineral level in the water supply.

Resin inside the water softener treatment tank (green arrow in our photo) contains salt molecules which are brought into contact with building water as it passes through the softener. The "resin" is made of tiny plastic beads of zeolite which are coated with salt or potassium ions. (Ions are molecules that have an electrical charge.)

As hard water which is to be treated flows through the resin or treatment tank (tan arrow in our photo at left) containing the salt-coated zeolite resin beads, salt molecules (NaCl) on the bead surface are "swapped" into the water displacing other mineral molecules that we're trying to remove from the water, such as Calcium (Ca or CaCO3) or Magnesium (Mg) that clog up pipes and create other problems. The Ca or Mg ions stick to the resin beads where they have replaced the NaCL.

The resulting "conditioned water" or "soft water" (blue arrow in our photo at above left) flows out of the treatment tank and into the building for use.

In sum, during that contact time as your building water passes through salty resin inside the treatment tank, the ion-exchange occurs to soften the water.

What is the Water Softener Recharge or Regeneration Cycle?

Periodically the water softener needs to recharge itself, a step which is controlled either manually by the homeowner or run automatically by a timer built into the water softener. Usually these steps involve pumping water backwards through the water softener and to a building drain, followed by dissolving salt tablets or crystals in a nearby holding tank and pumping the new salty water into the softener.

During a water softener regeneration or recharge cycle two things happen:

  1. Water is first pumped into the brine tank (the larger of the two water softener tanks in traditional installations) where it dissolves salt that is in the tank (you put it there) in the form of salt crystals or pellets.
  2. The salty backwash water is next pumped out of the brine tank and back through the water softener treatment tank (the smaller of the two water softener tanks) where it does two more things:
    1. The water softener backwash - regeneration cycle washes out the precipitated calcium and magnesium which have stuck to the zeolite bead surface - thus having been removed from the water supply,
    2. The salty backwash water passing through the water softener treatment tank it also re-charges the salt in its ion exchanger - salt molecules stick to the surface of the zeolite resin beads.

The salty water passing back through the treatment tank has given up some of its salt to regenerate the resin beads there and it has picked up the un-wanted calcium and magnesium that were previously removed from the building water as it passed through the same tank earlier. The water used during the regeneration cycle gallons is discharged through a drain tube into an approved destination like a drywell.

How often a water softener needs to backwash and recharge itself depends on two factors: how much water is used in the building and how hard the water is.

How much salt a water softener uses at its backwash cycle depends on the hardness of the water being processed.

Reader Question: Should water actually leave the water softener during a backwash cycle?

Never used a water softener before, went to do a backwash and regenerate. Should the water actually leave the softener and then refill because it sounds as though it wants to run but no water is leaving the tank and filling back up - Jhar1986 9/19/2012

Reply: yes. Here are the details:

  1. Jhar, reviewing from above,

    Water Softener Recharge or Regeneration Cycle: Periodically the water softener needs to recharge itself, a step which is controlled either manually by the homeowner or run automatically by a timer built into the water softener. Usually these steps involve pumping water backwards through the water softener and to a building drain, followed by dissolving salt tablets or crystals in a nearby holding tank and pumping the new salty water into the softener.

    During a water softener regeneration or recharge cycle two things happen:

    Water is first pumped into the brine tank (the larger of the two water softener tanks in traditional installations) where it dissolves salt that is in the tank (you put it there) in the form of salt crystals or pellets.
  2. The salty backwash water is next pumped out of the brine tank and back through the water softener treatment tank (the smaller of the two water softener tanks) where it does two more things:

The water softener backwash - regeneration cycle washes out the precipitated calcium and magnesium which have stuck to the zeolite bead surface - thus having been removed from the water supply,

The salty backwash water passing through the water softener treatment tank it also re-charges the salt in its ion exchanger - salt molecules stick to the surface of the zeolite resin beads.

So yes, water enters the brine tank, then flows back through the water softener and out it's drain during the regen cycle

Comparing Swap-in, Manual, Twin Tank & Automatic Water Softener or Water Conditioner Features

Map of hardness of water in areas of the U.S. - USEPA et als

Water softeners address these two variables and is regenerated or "recharged" by these means

What are the Controls on a Water Softener / Conditioner & What do They Do?

The water softener installer sets up the water softener control to specify

Some experts suspect that many homeowners use more salt and more frequent backwashing than the water usage and hardness require.

Details about how to set or adjust the water softener controls are at   SOFTENER ADJUSTMENT & CONTROLS.

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Continue reading at SOFTENER ADJUSTMENT & CONTROLS or select a topic from the More Reading links or topic ARTICLE INDEX shown below.

Or see INSTALLATION of WATER CONDITIONERS

Or see WATER SOFTENERS & CONDITIONERS - home

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HOW WATER SOFTENERS / CONDITIONERS WORK at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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