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Water Softeners

Scope

Water softeners reduce minerals in hard water but overly frequent recharging of the mineral tank can waste water.
Water softeners reduce minerals in hard water but overly frequent recharging of the mineral tank can waste water.

If a water softener is installed, it should be a demand-initiated regeneration system that is water- and salt-efficient.

All self-regenerating water softeners shall be certified to meet the most current standards for NSF International/ANSI 44 Residential Cation Exchange Water Softeners, including the voluntary efficiency rating standards in Section 7 – Mandatory Testing for Elective Claims for efficiency rated systems, which states that water softeners shall: 

  • Be a demand-initiated regeneration system (i.e., it must use a flow meter or water hardness sensor to initiate regeneration; devices that use time clock-initiated regeneration [fixed time schedule] do not qualify for the efficiency rating).
  • Have a rated salt efficiency of not less than 3,350 grains of total hardness exchange per pound of salt, based on sodium chloride (NaCl) equivalency (477 grams of total hardness exchange per kilogram of salt). 
  • Not generate more than 5.0 gallons of water per 1,000 grains of hardness removed during the service cycle (18.9 liters per 64.8 grams of total hardness removed).

See the Compliance Tab for related codes and standards requirements, and criteria to meet national programs such as DOE’s Zero Energy Ready Home program, ENERGY STAR Certified Homes, and Indoor airPLUS.

Description

Water softeners are common household appliances found in regions of the country where hard water (or water that contains a lot of dissolved calcium or magnesium) is prevalent. Hard water can cause scales to form on the inside of pipes, water heaters, and other appliances and equipment. Scales do not conduct heat well and can reduce the flow of water through pipes. Hard water also reduce soap's ability to lather and reacts with the soap to form a sticky coating on skin.

Hard water can be managed by softening or filtering the water. Water softeners are often used due to the high costs associated with filtration. The calcium and magnesium ions in the water are replaced with univalent hydrogen, sodium, or potassium ions (i.e., cation exchange). To achieve the ion replacement, the water in the house runs through a bed of small plastic beads or through a chemical matrix called zeolite. The zeolite is covered with hydrogen, sodium, or potassium ions. As the water flows past the hydrogen, sodium, or potassium ions, they swap places with the calcium and magnesium ions. Eventually, the zeolite contains nothing but calcium and magnesium, and at this point it stops softening the water. It is then time to regenerate the zeolite. Regeneration involves soaking the zeolite in a stream of concentrated brine, usually of sodium chloride or potassium chloride, or acid solution. The strong brine displaces all of the calcium and magnesium that has built up in the zeolite and replaces it with hydrogen, sodium, or potassium. The remaining brine plus all of the calcium and magnesium are flushed out through a drain pipe.

Figure showing the interior workings of a water softener.
Figure 1. Water softeners remove calcium and magnesium from hard water by sending it through a resin bead or zeolite matrix where the calcium and magnesium ions are exchanged with hydrogen, sodium, or potassium ions. Using controls to recharge the zeolite only when its depleted instead of on a calendar schedule can reduce water waste. (Courtesy of U.S. EPA WaterSense Program)

While the volume of water consumed by these fixtures during the regeneration phase has decreased significantly in recent years, water softeners still generate and discharge a significant volume of wastewater. To minimize the water consumption of these fixtures and reduce the amount of salt discharged into septic and sewer systems, the NSF/ANSI 44–Residential Water Softener Testing Standard and the Water Quality Association’s WQA S-100 Residential Water Softener Testing Standard include a voluntary set of requirements for efficiency-rated (ER) residential cation exchange water softeners. (These two standards are essentially identical. Therefore, a residential cation exchange water softener can be certified to either standard.)

All residential cation exchange water softeners sold in the United States must be certified to the general requirements of NSF/ANSI 44 (or WQA S-100). The voluntary efficiency requirements found in Section 7 of NSF/ANSI 44 are for manufacturers looking to differentiate and market their products as water- and sodium-efficient. Under Section 7, an ER system must meet the following criteria:

  • Be a demand-initiated regeneration (DIR) system. In other words, it must use a flow meter or water hardness sensor to initiate regeneration. Devices that use time clock-initiated regeneration (fixed time schedule) do not qualify for the efficiency rating. Softeners that use time clock-initiated regeneration automatically regenerate on a fixed time schedule set by the user (typically every four days to weekly). This can result in unnecessary regeneration during times of reduced use and waste large volumes of water.
  • Have a rated salt efficiency of not less than 3,350 grains of total hardness exchange per pound of salt, based on NaCl equivalency (477 grams of total hardness exchange per kilogram of salt).
  • Not generate more than 5.0 gallons of water per 1,000 grains of hardness removed during the service cycle (18.9 liters per 64.8 grams of total hardness removed).

Most manufacturers indicate on the product packaging and literature that their product meets the NSF/ANSI 44 Residential Cation Exchange Water Softeners Efficiency Rating. In addition, the following organizations that independently certify water softeners to the NSF/ANSI standards maintain a listing of products that meet the voluntary efficiency rating:

Ensuring Success

The inspector will verify through the manufacturer’s product specification sheet or product manual that the softener has been certified to meet NSF/ANSI 44 Residential Cation Exchange Water Softeners, including the voluntary efficiency rating standards in Section 7.

 

Climate

This guide is relevant to locations with hard water.  

Training

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Presentations

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Compliance

The Compliance tab contains both program and code information. Code language is excerpted and summarized below. For exact code language, refer to the applicable code, which may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

Environmental Protection Agency (EPA) WaterSense® New Home Specification

The EPA WaterSense New Home Specification states that:

If installed in the new home, self-regenerating water softeners shall be certified to meet NSF/ANSI 44 Residential Cation Exchange Water Softeners, including the voluntary efficiency rating standards in Section 7 – Mandatory testing for elective claims for efficiency rated systems, which states that water softeners shall:

  • Be a demand-initiated regeneration system (i.e., it must use a flow meter or water hardness sensor to initiate regeneration; devices that use time clock-initiated regeneration [fixed time schedule] do not qualify for the efficiency rating).
  • Have a rated salt efficiency of not less than 3,350 grains of total hardness exchange per pound of salt, based on sodium chloride (NaCl) equivalency (477 grams of total hardness exchange per kilogram of salt).
  • Not generate more than 5.0 gallons of water per 1,000 grains of hardness removed during the service cycle (18.9 liters per 64.8 grams of total hardness removed).

 

This Retrofit tab provides information that helps installers apply this “new home” guide to improvement projects for existing homes. This tab is organized with headings that mirror the new home tabs, such as “Scope,” “Description,” “Success,” etc. If there is no retrofit-specific information for a section, that heading is not included.

SCOPE
See the U.S. Department of Energy’s Standard Work Specifications (SWS) for more on water softening. DOE’s Standard Work Specifications describe practices to complete whole-house energy upgrades safely without injury or hazardous exposure in the section on Global Worker Safety

More Info.

Access to some references may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

Case Studies

None Available

References and Resources*

  1. Publication Date: June, 2017

    Resource that helps connect consumers with water treatment products that have been tested and certified to industry standards.

     

  2. Author(s): Nicholas Gerbis
    Organization(s): Home & Garden
    Publication Date: April, 2000

    Resource that explains how water softeners work to reduce scale.

  3. Author(s): U.S. Environmental Protection Agency
    Organization(s): EPA
    Publication Date: July, 2014

    Resource that provides WaterSense inspectors with guidance for verification of program requirements for water-efficient new homes under the U.S. Environmental Protection Agency’s (EPA’s) WaterSense program.

  4. Author(s): The Public Health and Safety Organization
    Organization(s): The Public Health and Safety Organization
    Publication Date: June, 2017

    Resource that helps connect consumers with NSF Certified Drinking Water Treatment Units.

  5. Author(s): Underwriters Laboratories LLC
    Organization(s): Underwriters Laboratories LLC
    Publication Date: June, 2017

    Resource that helps verify UL listing, classification, or recognition.

  6. Author(s): U.S. Environmental Protection Agency
    Organization(s): EPA
    Publication Date: July, 2014

    Resource to help builders better understand the WaterSense requirements for labeled homes and assist them in meeting the criteria so they can receive the label for their new construction.

  7. Author(s): U.S. Environmental Protection Agency
    Organization(s): EPA
    Publication Date: July, 2014

    Resource that provides a checklist of program criteria for water-efficient new homes under the U.S. Environmental Protection Agency’s (EPA’s) WaterSense program.

  8. Author(s): U.S. Environmental Protection Agency
    Organization(s): EPA
    Publication Date: July, 2014

    Resource that establishes the criteria for water-efficient new homes under the U.S. Environmental Protection Agency’s (EPA’s) WaterSense program.

Contributors to this Guide

The following authors and organizations contributed to the content in this Guide.

Last Updated: 06/24/2017