What Do NSF Standards Mean on Water Filter?

NSF 42/44/53/55/58/62/177 Is this the winning number for the NSF lottery?
Well not exactly, but if you know what these standards mean, you can be a winner every time!

We often take for granted that the quality of the water we want for washing our car doesn’t need to be of the same standard as what we want for the water we drink. We don’t think about the costs of processing the water that supplies our homes or businesses. While the water we use may be free at the source, it costs something to get it to us, and depending on the quality of water we want, those costs can vary greatly.

Cost-to-Benefit

As an extreme example, a semiconductor factory, or hospital may invest in expensive purification equipment to get ultra-pure water, but they surely wouldn’t use that water to flush the toilet. While it may be nice to have pure water for toilets, the cost of purifying the water would far outweigh any advantages gained.

On a more practical scale, it would be prohibitively costly to require a municipal water supplier to supply water completely free from unhealthy contaminants. So, to reach a cost-to-benefit balance, some Local, State or National laws require municipal suppliers to meet the Maximum Contaminant Level (MCL) for a broad range of recognized contaminants. While some contaminants may be allowed, what is allowed is deemed to be at a level low enough to not pose any major health risks.

Factors to be Considered for Water Quality Standards

Besides health risks, there are many other factors that can affect the quality of water. For example, hardness and alkalinity may not affect health but may cause corrosion or scale deposit in appliances and plumbing. On the other hand, most biological or petrol-chemical contaminants won’t affect appliances or plumbing but may affect health. Other contaminants may negatively affect the taste of water making it undesirable to drink.

As a result of this, NSF has a long list of standards that address these issues.

Below is a list of some of the most common NSF water certifications, explaining the water quality issue they address and the quality standards required to receive certification under each of these standards.

POU Filtration

Once the water has reached your home, there are a variety of water treatment systems that can further treat water at the point of use, (POU) to meet the desired standard for various uses. NSF tests to certify these systems to ensure these products meet the claimed standards.

NSF Water Quality Standards for Water Treatment Systems

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 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 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 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.