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HOW Water SOFTENERS WORK - Water Softener Operation: How Do Ion Exchange Water Softeners Work

Conventional 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). 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.

Resin inside the water softener 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 treatment tank 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 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.

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.

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.

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

• Offsite or "swap-in" water softeners: a water softener treatment tank is brought into the home and installed using quick-disconnect plumbing fittings. On a regular schedule a water treatment company comes by and swaps out the old treatment tank, installing a new one that has been regenerated or cleaned at their facility. This type of water softener does not use any electricity and has no controls other than a bypass valve. (We had one in our first home, maintained by Culligan™).
• Manual water softeners: manual backwash/regeneration cycle of the water softener initiated by the owner who is supposed to notice that the water feels "hard" (can't get a lather in the shower) or as part of maintenance say when the water softener has been shut down for a week or more
• Automatic regular periodic backwash/regeneration in the water softener accomplished by a clock timer attached to the water softener
• Automatic "as needed" backwash/regeneration in the water softener, controlled by a sensor in the (more costly) water softener monitors either water hardness (water hardness sensor) at the softener outlet pipe or the total volume of water used (water metering) and backwashes (regenerates) when needed.
• Twin-tank water softeners are available for installations (such as commercial) where 24-hour availability of soft water is needed. - IBC.

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

• How often the automatic periodic regeneration cycle should occur, such as once a week, once every other day, etc.
• What time of day the regeneration cycle should occur - typically at 2AM when people are unlikely to be using water
• How much water should be used during the water softener backwash - regeneration cycle - this is specified by adjusting the time-duration of the backwash cycle. Factory default is typically 10 minutes of backwash time. The cycle may be adjustable to a time ranging between 5 minutes and 30 minutes as needed. The number of gallons of water used during the water softener backwash cycle varies depending on the water pressure and flow rate in the building water supply piping.
  
  A rough guess would be a typical volume of about 30 gallons of water (3 gpm for 10 minutes) but could be as little as 10 gallons or as much as perhaps 150 gallons (5 gpm for 30 minutes). If your water softener is running longer than 30 minutes during a backwash cycle it may not be working properly.
• How much salt should be used during the water softener regeneration cycle

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 the water softener controls are at   SOFTENER ADJUSTMENT & CLEANING.

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WHAT CAN GO INTO TOILETS & DRAINS?
  DETECT HARD WATER
  MEASURE WATER HARDNESS
  HOW SOFTENERS WORK
  HEALTH RISKS & WATER SOFTENERS
  SALT OR WATER INTO SEPTIC
  REDUCE IMPACT OF SOFTENER
  SOFTENER ADJUSTMENT & CLEANING
  OTHER SOFTENER METHODS
  Winterize Water Softener & Treatment Equip
  Restoring Water Softener & Treatment Equip

• North Dakota Standards for Water Softeners, North Dakota General Authority Law, Chapter 62-04-08, Water Softener Units http://www.legis.nd.gov/information/acdata/pdf/62-04-08.pdf. "The objective of this chapter is to provide a standard of quality, capacity, and performance for water softener units. Water softener performance is to be based upon referee tests procedures described in section 62-04-08-09."
• Culligan Mark 10 Water Softener 1994-1998 Installation and Operating Instructions (covering models manufactured after 1995) (1-96) 01881948.pdf available from www.culligan.com
• Water Softeners, CMHC, Canadian Mortgage and Housing Corporation, cmhc-schl.gc.ca/en/co/maho/wawa/wawa_005.cfm - October 2008. Canada Mortgage and Housing Corporation acknowledges the contribution of Health Canada to the development of this document. For further questions regarding water treatment and water quality, contact Health Canada at watereau@hc-sc.gc.ca or call 613-957-2991 or 1-866-225-0709.
• "Commercial Water Softener Installation and Operating Instructions", IBC Filtration & Water Treatment Products (Australia) for commercial, industrial and residential application www.ibcwater.com.au (07) 3219 2233
• "Non electric water softener, Installation and Operating Instructions", IBC Filtration & Water Treatment Products (Australia), op.cit.
• Watts Industries of North Andover, Mass., provides its ZRO-4 under counter system intended to target the independent water dealer market.
• "Water Softener Twin Tank Installation and Operating Instructions", IBC Filtration & Water Treatment Products (Australia), op.cit.
• Our Water Hardness Table used at originated with but was edited and added to from http://www.bestfish.com/tips/110598.html and also from http://www.water-research.net/hardness.htm

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