Residential softening

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A review of residential water softening

Water softener overview

Many residential households use water softeners to remove hardness from water. Water softening can have benefits including extending the life of appliances, preventing scale on fixtures, reducing energy use in water heaters, and decreasing the amount of cleaning products needed. However, there are some negative environmental impacts such as increased water use, and chloride from the salt discharged into surface waters where it is harmful to aquatic plants and animals. Capital costs for water softeners vary widely depending on features and size. Professionals in the water quality industry can provide more detailed guidance and tailored recommendations. General features of water treatment options are described below for comparison but will vary by manufacturer, unit, and application.

Demand-initiated regeneration

Many older softener regenerations are time clock initiated, using electronic timers or clocks to recharge the resin at a pre-set time and day. This wastes salt and water because they regenerate whether or not regeneration is necessary. Most new softeners use a more sophisticated method called demand-initiated regeneration (DIR) where regeneration is based on the measured amount of water used. 

  • Cost: $-$$
  • Salt Use: 26 - 60% less salt than time clock softeners
  • Water treatment: Provides softened water
  • Maintenance: Clean tank every 5-10 years, check salt levels monthly
  • Water Use: 25 – 40% less water than time clock softeners

Twin tanks water softeners

Multi-tank systems will improve salt and water use efficiency. They allow for continuous soft water supply since no reserve capacity is needed in a dual-tank system, saving salt and water.

  • Cost: $ ~30% more than single tank softener
  • Salt Use: Up to 30% less salt than single tank softener
  • Water treatment: Provides continuous soft water
  • Maintenance: Clean brine tank every 5-10 years, check salt levels monthly
  • Water Use: 15% less water than single tank softener

Hardness sensors

Some of the most efficient softeners are equipped with sensors that measure the hardness and initiate regeneration and/or adjust settings for optimal performance. Softeners with hardness sensors are best suited for areas where hardness fluctuates (check with city staff).

  • Cost: $$-$$$ for softener with hardness sensor
  • Salt Use: Uses less salt
  • Water treatment: Provides softened water
  • Maintenance: Check softener manual
  • Water Use: May use less water

Counter-current regeneration

Down-flow or co-current regeneration is the more common type of regeneration. Co-current softeners require less maintenance where water contains iron or manganese. Up-flow or counter-current regeneration uses brine more efficiently; the brine flows in the opposite direction of the service flow through the resin that is least depleted to the resin that is most depleted. Less salt is needed for this process than co-current regeneration.

  • Cost: $-$$
  • Salt Use: Up to 40- 50% less salt than co-current softeners
  • Water treatment: Provides softened water
  • Maintenance: check salt levels monthly, refill; professional check every two-five years
  • Water Use: Up to 30% less water than co-current softeners

Water softener replacement

Water softeners become less efficient as they age. Replacing old household water softeners with newer models can improve salt efficiency. Over time and use, valves weaken, resin beads deteriorate, and softeners fail. Newer water softeners are designed to be more efficient.

  • Cost: $-$$ for new softener
  • Salt Use: up to ~50% less salt with new softener
  • Water treatment: Provides softened water
  • Maintenance: check salt levels monthly, refill; professional check every two-five years and when family size changes
  • Water Use: variable

Exchange program

In a water softener exchange service or program, a company delivers a recharged resin tank to the customer’s home. When the tank needs to be regenerated, it is removed by the service company and taken to a central facility for regeneration. Tanks are exchanged on a regular schedule based on estimated water use and water hardness.

  • Cost: $-$$
  • Salt Use: Will not reduce home salt use (salt is used to regenerate at central facility)
  • Water treatment: Provides softened water
  • Maintenance: No maintenance for homeowner, higher cost for tank delivery/exchange
  • Water Use: Will not reduce water use (water will be used at the central facility for regeneration)

Water softener alternatives (water conditioners, non-salt-based systems)

Water “softening” is the term generally used for removing calcium and magnesium by ion exchange – using salt. Ion exchange is by far the most common and most accepted process for scale control and for the reduction of residual compounds left after cleaning and bathing. While ion exchange media and the softener control systems are greatly improved, there are viable non-salt based alternatives available on the market.

Softening alternatives include several options that fall under the larger category of water conditioning. Some soften the water (remove the calcium and magnesium) and others do not but may inhibit scale formation by suspending the calcium and magnesium in the water. Reverse osmosis is a well proven technology but most of the other options are not as well proven. Carefully examine product claims before purchasing a device and check the reputation of the seller with the Better Business Bureau or similar resources. In Minnesota, water conditioning dealers and plumbers are licensed to install water conditioning units.

Reverse osmosis (RO)

Reverse osmosis (RO) technology uses a membrane and additional filters to remove dissolved solids and other contaminants from water. Whole house systems or small systems for drinking water are available.

  • Cost: $$$-$$$$ installed whole house system
  • Water treatment: Filter system, provides continuous soft water, removes contaminants
  • Maintenance: Regular filter change/less frequent membrane change
  • Water Use: High-uses up to 4+ gallons of water per gallon of filtered water

Capacitive deionization (CDI)

Capacitive Deionization (CDI) uses current to attract ions to the anode and cathode. No salt is used. This method reduces concentrations of all ions to minimize scale formation and remove almost all hardness.

  • Cost: $$$
  • Water treatment: provides continuous mostly soft water, except during backwash
  • Maintenance: Backwash, citric acid cleaning
  • Water Use: Backwash has 25% reject water

Electrically induced precipitation

Electrically induced precipitation is a conditioning technology that uses an applied current to induce the formation of "soft" scale on an electrode, reducing scale by approximately 50%.

  • Cost: $$-$$$
  • Water treatment: Descaler, reduces hard scale that builds up on fixtures and appliances
  • Maintenance: Requires backwash to clean the electrode
  • Water Use: Soft scale must be periodically backwashed, increasing water use

Nucleation assisted crystallization/Template assisted crystallization (TAC)

This technology uses resin beads to force hard ions in water to crystalize on the resin. When the crystals become large enough they are released as a fine dust in the water, preventing scale formation on surfaces. TAC systems generally require relatively clean input water. A filter may be needed to remove iron, manganese and sediment.

  • Cost: $
  • Water treatment: Descaler prevents up to 90% scale buildup
  • Maintenance: Requires replacement media every three years
  • Water Use: Uses no extra water


Chelation is a conditioning technology that uses a chelating agent (such as citric acid or EDTA) to tie up hardness ions, making them unable to form scale on fixtures and appliances. This technology may prevent scale buildup by up to 99% and may also remove existing scale. Chelation has not been well proven, especially for higher hardness levels (> 8-10 gpg), or if iron, dissolved oxygen, or dissolved silica are present.

  • Cost: $
  • Water treatment: Descaler
  • Maintenance: Filter changes every six to twelve months
  • Water Use: Uses no extra water


Magnetic water treatment is a controversial conditioning technology. It uses powerful magnets or electromagnetic devices wrapped around a pipe to create a magnetic field. As hard water passes through the magnetic field created by the device, it may precipitate out hard ions into a “soft scale” which prevents scale formation on fixtures and in appliances. Studies show mixed results on the effectiveness of this technology.

  • Cost: $
  • Water treatment: Descaler, may reduce scale formation up to 50%
  • Maintenance: none
  • Water Use: Uses no extra water

Radio waves

Technologies using radio waves to remove and prevent scale are relatively new. The unit is installed on the outside of a pipe. The conditioner sends an electrical signal from a ring of ferrites to the water inside the pipe causing the ions to suspend in the water as clusters thus preventing them from attaching to surfaces.

  • Cost: $
  • Water treatment: Descaler
  • Maintenance: none
  • Water Use: Uses no extra water


Water softening technologies

There are some products or actions that can improve the efficiency and life of water softeners. Some of these are discussed below.

Salt type

Regardless of labelling, all softener salt products contain chloride. While there are many salt products available, the base of these products is either sodium chloride or potassium chloride. Sodium chloride is the most commonly used salt in water softener brine tanks. It is widely available and is sold at comparatively lower prices than other salt products. Potassium chloride is used when there are health concerns with sodium intake.

  • Cost: Potassium chloride is 3 - 5x more expensive than sodium chloride
  • Salt Use: Potassium chloride is 15 to 30% less efficient than sodium chloride
  • Water treatment: Used in ion exchange water softeners to recharge resin
  • Maintenance: Will need to add salt more frequently with potassium chloride


Filters may be needed to remove contaminants in water including iron, manganese, hydrogen sulfide and sediment from well water and chlorine from city and well water. It is important to have your water tested to determine if you need a filter.

  • Cost: $ additional capital cost, $ filter media replacement costs
  • Salt Use: Reduces salt use. Removal of iron with a softener uses ~ 4x more sodium than used to remove hard ions.
  • Water treatment: Removes iron, manganese, hydrogen sulfide, sediment or chlorine depending on filter type
  • Maintenance: Filter media replacement • Water use: Degraded resin decreases water softener efficiency, filter backwash uses water
Iron, Manganese and Hydrogen Sulfide

Iron and manganese stain laundry and plumbing fixtures, add a metallic taste to water, reduce the efficiency of water softeners, and potentially build up in pipelines, water heaters, and water softeners. In general, water softeners may remove up to 3 mg per liter of iron in the water. For higher levels or more efficient operation, iron filters are recommended. If iron or manganese is not thoroughly removed from the resin beads, oxygen in the water oxidizes them, reducing capacity and efficiency. Many municipalities remove iron and manganese before distribution.

Activated carbon filters

Activated carbon filters are recommended for municipal water supplies treated with chlorine and well water if chlorine is used for disinfecting. Chlorine degrades resin beads. A chlorine concentration of 2 parts per million can reduce by half the life of resin beads. Removing chlorine significantly improves taste. Carbon filters also remove many other contaminants such including carcinogenic disinfection by-products, VOCs, and many pesticides.

Resin type

Water softeners include a resin tank containing resin beads. Resin beads are little porous, plastic spheres of polystyrene strings linked in a crisscross pattern. Resin with a higher % cross-linkage (10% vs. 8$) increases the resin beads durability and life-span. Over time resin beads break down or get clogged, reducing the capacity of the resin beads to trap hard minerals which results in more frequent regeneration, wasting water and salt. Quality resin can extend water softener life by 50 – 100%.

  • Cost: $ Better resin will cost more up front
  • Salt Use: Reduced due to less frequent regeneration needed for higher cross-link or newer resin
  • Water treatment: Provides softened water
  • Maintenance: Use resin bed cleaner every 3-12 months based on iron levels
  • Water Use: Quality resin will reduce water use by requiring fewer regeneration cycles

Blending Valve

Some people don’t like the slippery feeling of soft water. A blending valve is an accessory valve that mixes some hard water into the softened water to raise the hardness from 0 to usually about 2 grains per gallon.

  • Cost: $ valves are very inexpensive, a plumber may need to install
  • Salt use: Reduced only slightly
  • Water treatment: Added to a water softener to reduce slippery feel of soft water
  • Maintenance: Adjusted and tested periodically by a professional
  • Water use: No extra water used

Tank size

A properly sized water softener tank will improve the efficiency of salt and water use, while achieving a satisfactory soft water supply. A water softener that is too small will run out of soft water and need to regenerate more frequently. This increases wear on the water softener and reduces its lifespan. A water softener that is too big may cause channeling, limiting softening capacity. In both cases, improperly sized water softeners have a greater potential for using salt inefficiently. Water softeners should be sized to work three to five days without regeneration and designed to treat water without significant pressure loss.

Water softener and iron filter discharge effects on septic systems

Past studies showed a negative impact of water softener regeneration discharge on septic tanks. More recent research shows that discharge from more efficient water softeners do not have a negative impact on septic tanks and may have a positive impact. The key is “efficient” softeners. A water softener that has a timer-based regeneration controller or a softener that is not set correctly may have a negative impact on the septic tank. A set properly softener uses less salt and water. Studies have shown that the large volume of water used for regeneration of softeners, and especially for iron filters which use a lot of water for backflushing, may displace partially treated water in the septic tank and move it into the drainfield, potentially damaging the field. A septic system should be sized correctly to accommodate the water softener discharge and iron filter discharge (if needed) as well as other estimated household uses. Chloride in the softener discharge cannot be treated in the drainfield and will eventually end up in groundwater.

If needed, softener discharge may be rerouted directly to the distribution box or discharge basin for a reasonable cost ($) to prevent agitation of the layers in the septic tank. Iron filters could potentially increase maintenance costs of septic systems. Iron filter backwash places a volume load on the septic system and dilutes working bacteria. Backwash water can often be diverted to the surface or to a pond to reduce maintenance of the septic system. Check with the local jurisdiction to see if either of these plumbing changes is encouraged.

Chloride from home water softeners

Chloride levels in many surface waters are increasing and pose an emerging environmental concern, since elevated chloride levels are harmful to aquatic life. Minnesota has many lakes, rivers, and streams with chloride water quality impairments, and chloride levels in groundwater are also increasing, particularly in urban areas.

A major source of chloride is water softening. Most Minnesota homes have moderately hard to very hard water, and many use water softeners. Water softeners remove hardness which causes scale buildup in pipes, appliances and water fixtures, and deposits on glassware.

Ion-exchange water softeners use salt, usually sodium chloride, for recharging. In cities, the salty recharge water (brine) drains to the sanitary sewer where it travels to a wastewater treatment plant (WWTP). Unfortunately, it isn’t feasible for most WWTPs to remove chloride, which is dissolved in water. In areas served by septic systems the brine often discharges to the septic system, although this is not a recommended practice as large amounts of sodium chloride can be detrimental to the system.

Is your water hard?
Hardness Grains per gallon (gpg) calcium carbonate
Soft 0 - 3.5 gpg
Moderately hard 3.5 - 7 gpg
Hard 7 - 10.5 gpg
Very hard > 10.5 gpg


What can I do?

Determine if you need a softener

First, consider why you want or need soft water, and if you can get by without it. Hardness less than 5 - 7 grains per gallon (gpg) may be acceptable to many homeowners. If your drinking water is from a river, it is naturally softer and you probably don’t need a softener. If you have publicly supplied water, you can find your water hardness from the water utility or city. Some cities soften the water at the drinking water plant. Have your water tested by a professional or buy a kit and test it yourself.

Consider upgrading your softener

Replace a timer regenerated softener with a demand-initiated softener.

Make sure your softener is sized correctly

Softeners that are too small or too large for household water use are less efficient.

Soften only as necessary

Soften only indoor, hot water. Soften specific appliances, such as water heaters.

Conserve water

Practice water conservation to reduce softener regeneration and salt use (e.g. using low flush toilets, using high efficiency or front-loading washing machines, taking shorter showers, etc.)

Regularly maintain your softener

Review softener manual and check settings. Have the system optimized by a professional.

Remove high iron from well water

High iron can clog the resin, so use a test kit or consult a professional to measure iron levels. If iron levels are >3 ppm, consider installing an iron filter to increase efficiency and water softener life, although discharge should be diverted from septic systems.

Remove high chlorine from city water

Find out the chlorine level from your public water supply, since high chlorine can damage the resin. If chlorine is over 1 ppm, consider installing a chlorine filter to increase efficiency and water softener life.

High efficiency features that can reduce salt use

  • Efficiency rating of 4000 grains/lb salt or higher
  • Upflow or counter-current regeneration
  • Hardness sensors and water meters
  • Variable reserve
  • Regeneration with softened water
  • Twin tanks

Salt-less water conditioning

Salt-less systems are available-- most don’t remove water hardness, but may prevent scale build-up on fixtures and appliances. Some are not well proven, so carefully examine product claims before purchasing.

Water softening/conditioning options for residential users