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Water Softeners based on Ion Exchange Units are effective at reducing: 

  • calcium, magnesium
  •  (some) inorganic iron, nitrate

Categorizing Hardness:

Suffice to say that there are several categorizations of hardness.  The US Department of the Interior has produced a simple, easy to read chart:


Maintenance of cation exchange units is largely confined to restocking the salt supply for the brine solution. With manual and semiautomatic models, the consumer will also have to start the regeneration cycle. Typically 6 - 7 pounds of salt (sodium chloride) per cubic foot of IE resin are used during the regeneration cycle. Salt is cheap,  heavy, and needs to be filled into a container usually about 30-40 " high. Monthly operating expenses range from $3 to $13 if sodium chloride (salt) is used and from $5 to $24 if potassium permanganate is used.  Consider maintenance costs.

If not regenerated on a regular basis the resin bed may become contaminated with slime or impurities, solidify  and become unusable.  If this happens, the resin must be replaced with new material. Consider maintenance

If the water is cloudy or otherwise discolored, it is likely that some, or many, of the contaminants are in a solid form. Solid particles are not removed by Ion Exchange and can clog the treatment media. Consider testing and adding mechanical filtration to remove suspended contaminants.

Most units are not recommended for concentration of iron above 3 ppm (ratings apply to ferrous iron ONLY) as resins can become clogged with iron if the raw water contains a high concentration of dissolved iron. Backwashing or reversing the normal flow of water through the treatment unit may be required to remove the iron. If Iron is a problem special additives can be included in the brine regenerating solution to help minimize this condition. Consider your water test results and maintenance costs.

High concentrations of dissolved hydrogen sulphide also can foul the resin bed of an ion exchange water softener. When hydrogen sulphide odor occurs in treated water (softened or filtered) and no hydrogen sulphide is detected in the non-treated water, it usually indicates the presence of some form of sulfate-reducing bacteria in the system. Water softeners provide a convenient environment for these bacteria to grow. A "salt-loving" bacteria, that uses sulfates as an energy source, may produce a black slime inside water softeners.

While there is controversy concerning disposal of the waste brines into septic systems, no credible proof of problems with softener disposal into septic systems has been published that we are aware of.  Studies by the Water Quality Association indicate that waste brine and purged contaminants do not injure leach fields or septic tanks. 

Softening hard water can reduce the quantity of cleaning products needed by as much as 50 percent. The life of the water heater, plumbing system and water-using appliances may be extended.  Of additional benefit are the better results in laundry, dishwashing, and personal grooming. Consider other indirect savings

As mentioned above softeners need to be recharged below are some of the differences between some of the automatic and semi-automatic controls available:

  • Water softeners with CLOCK-TYPE (TIMER) controls regenerate according to a fixed time schedule (every 3 days, or 6 days, etc.) regardless of the amount of water actually used in the home. This is based on a "guess" of how much water you might use daily. Often these units regenerate too soon, wasting salt. Or too late...allowing  hard water into the home.
  • Water softeners with SIMPLE METER-TYPE CONTROLS regenerate after a fixed amount of water has passed through the meter. This is a better method than the timer softeners, since it is based on actual water usage. However, these units have a preset calculated reserve capacity to carry through the day until the unit regenerates at night. If your usage increases, the reserve capacity may not be enough and you can run out of soft water.
  • Water softeners with SENSORS have an electronic sensing device imbedded in a fixed point low in the softener resin. Since the resin exhausts from top to bottom, when the sensor detects hard water, it signals the valve to recharge that night (again, usually after midnight). This design, like the meter, is using actual water usage to determine recharge intervals, so it is an improvement over the timer type. The "reserve capacity"
    is the amount of resin left below the sensor. Since the sensor is in a fixed position, the reserve capacity is a fixed amount.

    A final note about controls; while sensor driven electronics are the most efficient, when they fail they may be costly to replace or require the unit to be removed and fixed off-site.

Water Conditioner Valve Styles

  • Hydraulic; powered by the water pressure within the system.
  • Cam; an electric motor driven cam rotates and actuates valves
  • Solenoid; electric solenoids actuate valves 

Sizing of Softeners can be confusing. First, the capacity of the resin media will deteriorate over time due to contaminants. The best method of comparing softener capacity is to consider the number of cubic feet of resin and the resin used. Measurement of softeners by grains of removal capacity may be misleading.  This is due to the relationship to the amount of salt used to regenerate the media to the grains of hardness that may be removed.  A softener can be regenerated with 25 pounds of salt or it may be regenerated with as little as 5 pounds of salt with effectual grains removal capability 150% of the same media. Simple math shows that you use 5 times the amount of salt to get only 1.5 times improvement in capacity.  A costly waste of salt! Your water conditioner will last for years, take your time to consider the merits of one over the other.

Most common softener resins are made of polystyrene in the form of porous beads.  Resin bead size is referred to mesh size.  Good resins range from 16 to 40 mesh. and shape, Resin bead shape is also important, beads should be perfect spheres and not include broken material because broken and deformed beads can get past the distributor into the water system with a resultant loss of capacity over time. Resins used within conditioners are not the same as the manufactured softener resins and look like anythng from course smooth sand sharp shards of rock crystals. Ask questions, ask look at the media.

Health Consideration:

The major disadvantage of water softeners may be that they remove calcium and magnesium and substitute sodium. There is a difference between organic (edible and digestible) and inorganic (mineral) matter.  Our bodies have limited ability to metabolize the inorganic calcium, manganese and iron in the water.  However, the sodium added to softened water is normally a relatively small fraction of the sodium intake from other dietary sources is able to be metabolized and is probably not a problem for healthy people. However, people on restricted salt diets should consult their physicians before using softened water from ion exchange units for drinking and cooking. To remove the sodium problem Potassium permanganate, a salt substitute is available. 

How much will I use:

This simple chart may help you estimate the amount of material necessary to regenerate a IE.  

Hardness Removed

Sodium (Na+ or Potassium (K+) added

10 mg/L as CaC03
10 mg/L as CaC03
 Sodium (Na+) added = 4.6 mg/L
 Potassium (K+) added = 7.6 mg/L 

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Last modified: September 21, 2017