Drinking Water Treatment Systems

    Scope Images
    Image
    A water softener collects water, filters it to remove minerals, and then sends it to the home's plumbing distribution system
    Scope

    If a drinking water treatment system is installed, it should waste no more than 15 gallons of water for every 100 gallons of water processed. These systems shall yield at least 85 gallons of treated water for each 100 gallons of water processed.

    Drinking water systems, if installed, shall be certified to meet applicable National Sanitation Foundation/American National Standards Institute (NSF/ANSI) standards, which are:

    • NSF/ANSI 42 Drinking Water Treatment Units – Aesthetic Effects
    • NSF/ANSI 53 Drinking Water Treatment Units – Health Effects
    • NSF/ANSI 55 Ultraviolet Microbiological Water Treatment Systems
    • NSF/ANSI 58 Reverse Osmosis Drinking Water Treatment Systems
    • NSF/ANSI 62 Drinking Water Distillation Systems

    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

    Public water suppliers must meet federal and state safe drinking water criteria to ensure water is safe to drink without additional treatment. Public water suppliers must notify consumers if a contaminant affecting health is found to exceed the criteria. In some cases, the supplier may be required to provide an alternate water supply. Private water supplies, on the other hand, are not regulated or tested. Individuals with private wells are responsible for protecting the water supply from contamination, testing the water quality, and selecting treatment if needed.

    To select an appropriate treatment system, a builder should know which contaminants or water properties the treatment system will address. There is no single device or method that removes all contaminants or solves every water problem, and no single test to determine if water requires treatment. Though most water treatment dealers can provide free in-home or laboratory tests, the tests normally are for nuisance contaminants such as hardness, pH, iron, manganese, sulfur, and total dissolved solids. Occasionally, a dealer may test for nitrate. Seldom does any test include all the contaminants covered by the Safe Drinking Water Act (SDWA). An example of a water softener for treating hardness is shown in Figure 1.

     

    Figure showing the interior workings of a water softener.
    Figure 1. A water softener collects water, filters it to remove minerals, and then sends it to the home's plumbing distribution system (Courtesy of U.S. EPA WaterSense).

     

    Most nuisance problems such as iron, manganese, hardness, pH, and odor require treatment at the point of entry of the water in the house. Some contaminants that affect health such as nitrate and lead are a concern only for water used for drinking or cooking, so point-of-use equipment at a separate tap that treats water only where it will be used for that purpose may be adequate. Bacteria and some organic contaminants will require point-of-entry equipment to prevent exposure during bathing or other water uses.

    Most residential drinking water treatment systems are at or close to 100% efficient. This means that one gallon of usable water is produced for every gallon of water that is treated, so they easily meet the 85 percent efficiency rating. One notable exception is reverse osmosis treatment systems. While useful for many reasons, reverse osmosis treatment inherently involves some amount of reject water that is not able to permeate the membrane. So it is important to confirm that these system meet the 85 percent efficiency rating, meaning that at least 0.85 gallons of usable water is produced for every gallon of water treated.

    NSF International has developed the following standards that apply to drinking water treatment systems:

    • NSF/ANSI 42 Drinking Water Treatment Units – Aesthetic Effects
    • NSF/ANSI 53 Drinking Water Treatment Units – Health Effects
    • NSF/ANSI 55 Ultraviolet Microbiological Water Treatment Systems
    • NSF/ANSI 58 Reverse Osmosis Drinking Water Treatment Systems
    • NSF/ANSI 62 Drinking Water Distillation Systems

    Products that have been tested or evaluated by NSF to meet the minimum requirements are entitled to display the NSF listing mark on the products or in advertising literature for products. Models that meet the applicable standard are included in a listing published twice annually.

    Visit the NSF website to find certified models: https://basc.pnnl.gov/library/list-nfpa-codes-standards.

    Ensuring Success

    The inspector will verify through manufacturer product literature that the installed drinking water treatment system meets the applicable NSF/ANSI standard and yields at least 85 gallons of treated water for each 100 gallons of water processed.

    To determine if a drinking water treatment system meets the applicable NSF/ANSI standard and has an 85 percent minimum rating, check the manufacturer’s product literature. Suppliers should also be able identify systems that meet this specification.

    Nearly all water treatment devices require some maintenance, monitoring, and/or testing to evaluate and ensure proper operation. Builders should ensure that the appropriate information is obtained from the manufacturer and provided to the homeowner.

    Climate

    No climate specific information applies.

    Right and Wrong Images
    Image
    The Durable Energy home is equipped with a water filtration system, which uses ultrafine membranes and carbon filters to filter city water or harvested rainwater to “bottled water-quality” for drinking water in the disaster-resilient home.
    The Durable Energy home is equipped with a water filtration system, which uses ultrafine membranes and carbon filters to filter city water or harvested rainwater to “bottled water-quality” for drinking water in the disaster-resilient home.

    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:

    Drinking water systems, if installed, shall be certified to meet applicable NSF/ANSI standards, which are:

    • NSF/ANSI 42 Drinking Water Treatment Units – Aesthetic Effects
    • NSF/ANSI 53 Drinking Water Treatment Units – Health Effects
    • NSF/ANSI 55 Ultraviolet Microbiological Water Treatment Systems
    • NSF/ANSI 58 Reverse Osmosis Drinking Water Treatment Systems
    • NSF/ANSI 62 Drinking Water Distillation Systems

    Such systems shall yield at least 85 gallons of treated water for each 100 gallons of water processed.

    Existing Homes

    Guidance for the measures described in this guide is applicable to both new and existing homes.

    DOE’s Standard Work Specifications describes 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.

    References and Resources*
    Author(s)
    U.S. Environmental Protection Agency
    Organization(s)
    EPA
    Publication Date
    Description
    PDF detailing the inspection and verification guidance for WaterSense labeled new homes including indoor and outdoor efficiency requirements, and homeowner and building management education.
    Author(s)
    The Public Health and Safety Organization
    Organization(s)
    The Public Health and Safety Organization
    Publication Date
    Description
    Resource that helps connect consumers with NSF Certified Drinking Water Treatment Units.
    Author(s)
    U.S. Environmental Protection Agency
    Organization(s)
    EPA
    Publication Date
    Description
    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.
    Author(s)
    U.S. Environmental Protection Agency
    Organization(s)
    EPA
    Publication Date
    Description
    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.
    Author(s)
    U.S. Environmental Protection Agency
    Organization(s)
    EPA
    Publication Date
    Description
    Resource that establishes the criteria for water-efficient new homes under the U.S. Environmental Protection Agency’s (EPA’s) WaterSense program.
    Author(s)
    Virginia Cooperative Extension,
    Virginia Tech,
    Virginia State University
    Organization(s)
    Virginia Cooperative Extension,
    Virginia Tech,
    VSU
    Publication Date
    Description
    Report describing filtration, distillation, and disinfection methods of water treatment.
    *For non-dated media, such as websites, the date listed is the date accessed.
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