How do you know if you need a water filter or a water purification or treatment system? What can you do to find the best filter for your home and where do you start? We have these helpful and important steps to find the right water treatment solution for your home. We test filters and treatment systems for safety and performance to provide assurance that a certified product will do what it says it is going to do.

Step 1: Find Out What Is In Your Water

If you are wondering what contaminants may be in your water, you can start by getting a copy of your water quality report (called a CCR or consumer confident report) from your local water utility/authority (in the U.S. and some cities in Canada). If you are unable to get your report or if you have a private well, you may want to consider having your water independently tested.

Step 2: Decide What Contaminants You Want to Reduce

Once you know what contaminants are in your water, you can better find a treatment solution that is certified to address your water quality concerns.

It’s important to understand that not all filters can reduce all contaminants. Based on the water report or your water testing results, you can decide what contaminants you want to reduce in your drinking water. NSF’s contaminant reductions claims guide will help you to locate products that are certified to reduce specific contaminants.

Step 3: Compare Options for Water Treatment

A number of water treatment solutions are available. They range from whole-house systems that treat all the water in your home, to filters for specific areas such as the kitchen faucet, to more portable solutions such as a water pitcher or even countertop filters. Some reduce only one contaminant while others reduce many.

  • Point-of-use (POU) systems treat the water where you drink or use your water, and include water pitchers, faucet filters and reverse osmosis (RO) systems.
  • Whole-house/point-of-entry (POE) systems treat the water as it enters a residence. They are usually installed near the water meter (municipal) or pressurized storage tank (well water). Whole-house treatment systems include UV microbiological systems, water softeners or whole-house filters for chlorine, taste, odor and particulates.

Visit our listings for NSF-certified versions of these products:

Point-of-Use Filters

Whole-House Filters

Additional Information

What Are NSF’s Drinking Water Standards?

NSF certifies drinking water filters to standards applicable to each type of treatment option. You may notice the NSF mark on a product along with numbers such as NSF/ANSI 53 or NSF/ANSI 42, which refer to the standard to which the filter has been certified. Manufacturers choose which contaminants their product will reduce and NSF International verifies that their filter will do what it says it is going to do. Because these standards allow manufacturers to certify their products to reduce a variety of contaminants, it’s important to check the packaging for both the standard name (such as NSF/ANSI 53 or NSF/ANSI 58) AND a claim for specific contaminant reduction such as lead.

Replacing Your Filter

Once you have decided on a home water treatment system, it will need regular maintenance to operate properly. Remember to replace your filter when required. Some filters have indicator lights and some may recommend time ranges for replacement. Familiarize yourself with the replacement requirements of your water treatment system. Be sure to include the ongoing cost of replacement filters in your final budget for a home water treatment solution.

While no federal regulations exist for residential water treatment filters, purifiers and reverse osmosis systems, voluntary national standards and NSF International protocols have been developed that establish minimum requirements for the safety and performance of these products to treat drinking water. The standards and protocols are explained in detail below. The numbers in the names reflect the order in which the standard or protocol was developed and are not a ranking or rating system.

  • NSF/ANSI 42
    Filters are certified to reduce aesthetic impurities such as chlorine and taste/odor. These can be point-of-use (under the sink, water pitcher, etc.) or point-of-entry (whole house) treatment systems.
  • NSF/ANSI 53
    Filters are certified to reduce a contaminant with a health effect. Health effects are set in this standard as regulated by the U.S. Environmental Protection Agency (EPA) and Health Canada. Both standards 42 and 53 cover adsorption/filtration which is a process that occurs when liquid, gas or dissolved/suspended matter adheres to the surface of, or in the pores of, an adsorbent media. Carbon filters are an example of this type of product.
  • NSF/ANSI 44
    Water softeners use a cation exchange resin that is regenerated with sodium or potassium chloride. The softener reduces hardness caused by calcium and magnesium ions and replaces them with sodium or potassium ions.
  • NSF/ANSI 55
    Ultraviolet treatment systems use ultraviolet light to inactivate or kill bacteria, viruses and cysts in contaminated water (Class A systems) or to reduce the amount of non-disease causing bacteria in disinfected drinking water (Class B).
  • NSF/ANSI 58
    Reverse osmosis systems incorporate a process that uses reverse pressure to force water through a semi-permeable membrane. Most reverse osmosis systems incorporate one or more additional filters on either side of the membrane. These systems reduce contaminants that are regulated by Health Canada and EPA.
  • NSF/ANSI 62
    Distillation systems heat water to the boiling point, and then collect the water vapor as it condenses, leaving behind contaminants such as heavy metals. Some contaminants that convert readily into gases, such as volatile organic chemicals, can carry over with the water vapor.
  • NSF/ANSI 177
    Shower filters attach directly to the pipe just in front of the homeowner’s showerhead and are certified to only reduce free available chlorine.
  • NSF/ANSI 244
    The filters covered by this standard are intended for use only on public water supplies that have been treated or that are determined to be microbiologically safe. These filters are only intended for protection against intermittent microbiological contamination of otherwise safe drinking water. For example, prior to the issuance of a boil water advisory, you can be assured that your filtration system is protecting you from intermittent microbiological contamination. The standard also includes material safety and structural integrity, similar to other NSF/ANSI drinking water treatment unit standards. Manufacturers can claim bacteria, viruses and cysts reduction for their filtration system.
  • NSF/ANSI 401
    Treatment systems for emerging contaminants include both point-of-use and point-of-entry systems that have been verified to reduce one or more of 15 emerging contaminants from drinking water. These emerging contaminants can be pharmaceuticals or chemicals not yet regulated by the EPA or Health Canada.
  • NSF P231
    Microbiological water purifiers are certified for health and sanitation based on the recommendations of the EPA’s Task Force Report, Guide Standard and Protocol for Testing Microbiological Water Purifiers (1987) (Annex B).

Keep in mind that certification to an NSF/ANSI standard or protocol does not mean that a filter, purifier or treatment system will reduce all possible contaminants. It’s important to verify that the filter, purifier or treatment system is certified to the applicable standard for the reduction of the contaminants of most concern to you or your family.