Water Filtration Technology

Choosing the Right Water Filtration System for You

Water filtration systems are a critical component of the home, especially in areas with known water quality issues.

Builders, developers, and owners of affordable housing can help create safer homes by ensuring that water filtration devices are included in plumbing as needed based on the presence of chemicals and pollutants that are found in the tap water. The chemicals found in water, and the concentrations at which they are found, vary based on one’s location and water supply source. Checking available resources such as EWG’s Database or Consumer Confidence Reports from the local utility are easy and free first steps to gather information about water quality. Those on private wells should get their well tested. Investigate whether the home has lead service lines, or lead pipes in the case of older buildings. For the most detailed information, test the tap water to identify potential hazards based on contaminants that could be found in the area, based on geography and proximity to industries. This includes not only lead but also other potential hazards like arsenic, bacteria, nitrates, and various industrial chemicals. Understanding these factors allows for the selection of appropriate filtration technologies and corresponding NSF/ANSI certifications for chemical reductions. 

 

Choosing a Water Filter Product 

Once you have information on what chemicals are in the tap or well water, consider the variety of water filters by system type, filtration technology, and NSF/ANSI certification paired with your budget and needs.  

 

Filter Maintenance 

To protect against contaminants, you must maintain your filter according to the manufacturer's instructions. If filters exceed their capacity, they may release accumulated contaminants back into your water, increasing the exposure.  

 

Understanding Water Filtration Systems and Processes 

System Types: Point of Use and Point of Entry 

Point of Use Filters - These filters treat water at a single tap, making them ideal for drinking and cooking. They are generally more affordable and easier to maintain. Point-of-use filters must be replaced according to the manufacturer’s instructions to remain effective and to prevent further  contamination from the used filter.  

  • Pitcher – A pitcher that is filled at the sink, filtering water as it passes through the filter into the pitcher. It is low-cost, low-maintenance, and easy to use but provides smaller amounts of filtered water at a time. 

  • Faucet Mounted – A small filter attached to the end of a faucet. It filters water as it flows through the faucet, offering easier installation and use with a higher water volume than pitchers. Faucet-mounted filters are grouped with countertop filters in our database. 

  • Countertop – A system that sits on the counter and connects to the faucet. Water passes through the filter and is dispensed from a dedicated faucet. This system provides more water than faucet-mounted filters but occupies counter space. 

  • Under-Sink – Installed beneath the sink, this filter connects to the plumbing. It saves counter space and provides a larger volume of water but requires altering the plumbing, sometimes requiring professional installation. 

  • Shower Filters- Attached to the showerhead, these filters remove chlorine and other contaminants from shower water. They are easy to install, help improve skin and hair health by reducing exposure to harsh chemicals and require regular filter replacements. 

If a building’s internal plumbing is comprised of lead pipes, or if the faucet fixture itself contains lead, countertop water filters or pitchers that are certified for lead reduction should be used to treat water, while the lead pipes and faucets are arranged to be replaced.  

 

Whole House (Point-of-Entry) Filters  

These systems are installed at the main water line, filtering all water entering the building. They are commonly used in commercial settings, homes with well water, or heavily polluted water sources, ensuring all water sources in the building provide filtered water. Whole house systems require professional installation due to significant plumbing modifications. Point-of-entry filters require replacement according to the manufacturer’s instructions to remain effective and to prevent further contamination from the used filter. 

If a building’s internal plumbing is comprised of pipes or faucets containing lead, point-of-entry water filters are not recommended as they would not be able to filter all lead as the water leaves the tap.  

Filtration Technology

These charts show some common types of water filtration systems and processes.  To test your water for various chemicals and bacteria, contact your local health department or follow the EPA’s home water testing guide

Filtration Technology 

Filtration Process 

Type of System 

Benefits   

Costs 

Activated Carbon and Granulated Activated Carbon 

Contaminants are removed through adsorption, where contaminants are attracted to the surface of the activated carbon and held to it 

Pitcher, Faucet, Counter, Under-Sink, Whole House 

Removes or reduces lead and arsenic; improves taste and odor of water; low upfront cost and no installation cost; portable 

Price and installation costs for systems go up with size; smaller systems need more filter changes 

Reverse Osmosis  

Semipermeable membrane that blocks particles larger than water molecules 

Counter, Under-Sink, Whole House 

Removes most unwanted contaminants including lead, arsenic, and perchlorates 

The filtration process wastes water; removes good minerals along with contaminants; cost of system goes up with size, filter quality 

Distillation 

This filter process heats water to vaporize it and then condenses the steam back into water 

Counter, Floor 

Removes chemicals that have higher boiling points than water - lead, arsenic, heavy metals, fluorides, and bacteria 

Energy inefficient; systems can be large and expensive; removes good minerals along with contaminants   

Ultraviolet (UV) 

Uses ultraviolet light to kill bacteria and other microorganisms 

Whole House, Portable 

Does not use heat or chemicals to remove contaminants; low maintenance 

Cannot remove chemical contaminants and works best in addition to other filtration; sensitive to discoloration in water  

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wide view of person writing a clip board regarding the manufacturing of products

Find Manufacturers

U.S. manufacturers of water filters can be found on Building Clean's database.

NSF/ANSI Certification

NSF/ANSI certification is awarded by NSF International, an independent, non-profit organization dedicated to public health and safety standards. NSF works with the American National Standards Institute (ANSI) to develop the standards. This certification ensures that a water filter has been tested and meets specific performance standards for contaminant reduction.  

When a filter is NSF/ANSI certified, it means it has been independently verified to effectively reduce contaminants to safe levels as specified by the certification standard. Manufacturers choose from a list of pollutants categorized under each NSF/ANSI Certification category and become certified to meet reduction levels for those specific chemicals. The pollutants or chemicals that a filter has been certified to remove will be communicated to the consumer via the product’s packaging or specification sheets. For example, a pitcher water filter certified to NSF/ANSI 53 for lead, copper, and arsenic will advertise itselves as such and meet no other reduction requirements for other chemicals that are grouped in NSF/ANSI 53. Every filter must be checked for the pollutants that they are certified to reduce to NSF/ANSI’s threshold.  

Certain water filtration products may be advertised as “tested to NSF/ANSI Standard,” but truly NSF certified products will say “certified to meet NSF standard.” Products that do not say “certified to meet NSF standard” mean that they are not actually third-party certified and therefore, cannot be verified or wholly trusted to meet reduction claims.  

 

NSF/ANSI Certification Descriptions 

The following NSF/ANSI Certifications are commonly used to improve the health and quality of drinking water. It is recommended to search for water filters that meet the specific chemical reductions that are present in your water. To search for water filters that remove or reduce  specific chemicals, visit the NSF/ANSI Certified Drinking Water Treatment Units Database. Verify which pollutants each filter is certified to reduce by checking the manufacturer’s product information for each water filtration device. 

NSF/ANSI 42 - Aesthetic Effects 

Focuses on improving the taste, odor, and clarity of drinking water. It verifies that the filter effectively reduces aesthetic impurities. 

Includes: Chlorine, taste, odor, particulates, and certain non-health-related contaminants 

Does not include: Health-related contaminants (lead, VOCs) 

NSF/ANSI 53 - Health Effects 

This standard addresses filters designed to reduce contaminants that are known to pose health risks.  

Includes: Heavy metals (lead, cadmium, arsenic, mercury), VOCs, cysts, PFOA and PFAS, asbestos, and other health-related contaminants 

Does not include: Aesthetic contaminants (chlorine taste and odor) 

NSF/ANSI 58 - Health Effects for Reverse Osmosis 

Specifically for reverse osmosis systems, this certification ensures the reduction of health-related contaminants selected by the product manufacturer. 

Includes: Heavy metals (lead, cadmium, arsenic, mercury), VOCs, cysts, PFOA and PFAS, asbestos, and other health-related contaminants 

Does not include: Aesthetic contaminants (unless specifically tested for) 

NSF 177 - Shower Filters 

This certification is for shower filters that reduce chlorine from water. 

Includes: Chlorine 

Does not include: Health-related contaminants (lead, VOCs, bacteria) 

NSF/ANSI 401 - Emerging/Incidental Contaminants 

This standard covers filters that reduce select emerging contaminants found in water at trace levels. It addresses newer, less commonly regulated substances that can still impact water quality. 

Includes: Pharmaceuticals, pesticides, herbicides, chemicals used as flame retardants, and detergents that have been found at trace levels in drinking water 

Does not include: Traditional health-related contaminants (lead, cysts) 

NSF P231 - Microbiological Water Purifiers 

This certification ensures that microbiological water purifiers effectively remove selected microbiological contamination from drinking water. It is designed for systems intended for health protection in areas with microbial water contamination.  

Includes: Bacteria, viruses, and cysts 

Does not include: Chemical contaminants (lead, chlorine) 

NSF 55 - Ultraviolet Microbiological Water Treatment Systems 

This standard applies to UV treatment systems that disinfect water by reducing microbial contaminants such as bacteria, viruses, and cysts. It ensures the system effectively uses UV light to inactivate select harmful microorganisms. 

Includes: Bacteria, viruses, and cysts 

Does not include: Chemical contaminants (lead, chlorine, VOCs) 

NSF 62 - Drinking Water Distillation Systems 

For distillation systems that remove a wide range of contaminants, including inorganic substances, heavy metals, and microorganisms. 

Includes: Inorganic contaminants (lead, nitrate), microorganisms 

Does not include: Volatile organic compounds (unless combined with activated carbon)