What Is NSF/ANSI 44? The Water Softener Standard
NSF/ANSI 44Cation Exchange Water Softeners
The NSF/ANSI standard for salt-based (cation exchange) water softeners, which verifies a model's rated hardness capacity and, when claimed, its salt efficiency.
- NSF/ANSI 42Aesthetic effects: taste, odor, particlesChlorine, chloramine, taste and odor, particulates, zincPitchers, faucet, under-sink, fridge and whole-house filters
- NSF/ANSI 53Contaminants with health effectsLead, cysts, VOCs, mercury, PFOA/PFOSPitchers, faucet, countertop, under-sink and fridge filters
- NSF/ANSI 58Reverse osmosis drinking water systemsTDS (required); optional claims such as lead, fluoride, arsenic, nitrateReverse osmosis systems, mostly under-sink
- NSF/ANSI 401Emerging compounds and incidental contaminantsIbuprofen, BPA, DEET, some herbicides, microplasticsPitchers, faucet, under-sink and fridge filters
- NSF/ANSI 44Cation exchange (salt-based) water softenersHardness, salt efficiency, barium, radium 226/228Whole-house water softeners
- NSF/ANSI 55Ultraviolet (UV) systems for microbesClass A: bacteria, viruses, cysts; Class B: nuisance microbesWhole-house and point-of-use UV systems
- NSF/ANSI 177Shower filters, aesthetic effects onlyFree available chlorineShower filters
At a glance
- Official name
- Cation Exchange Water Softeners
- Claims listed
- Hardness reduction, efficiency rating, barium, radium 226/228
- Efficiency rated
- At least 3,350 grains of hardness removed per pound of salt
- Products
- Whole-house (point-of-entry) water softeners
- Not covered
- Salt-free conditioners and shower filters
You don’t need a softener unless scale, spots and soap scum bother you; our hard water guide explains why hard water isn’t a health problem. If you do buy one, NSF/ANSI 44 is how you check that it softens as well as the maker says.
What does NSF/ANSI 44 certify?
On NSF’s listings for the standard, the claims are:
- Hardness reduction: the softener’s published capacity ratings for removing hardness have been verified.
- Efficiency rated: the softener removes at least 3,350 grains of hardness per pound of regenerating salt and uses no more than 5 gallons of regeneration water per 1,000 grains removed.
- Barium and radium 226/228 reduction: extra claims some models carry, useful if a water test shows them.
Nearly all of the listed products are point-of-entry systems, treating the water for the whole house. The Minnesota Department of Health lists calcium, magnesium, iron, manganese, copper and radium among what cation exchange softening is designed to remove, and Wisconsin’s health department points well owners to NSF/ANSI 44 softeners for manganese.
Do certified softeners add sodium to water?
Yes, when they regenerate with sodium chloride. Wisconsin notes that softener salt can raise the sodium in your water, a concern if you’re on a low- or no-sodium diet, and Minnesota adds that potassium chloride can be used instead. Certification doesn’t change this; it’s how cation exchange works. The hard water guide covers sodium, salt use and the other trade-offs.
Are salt-free conditioners certified to NSF/ANSI 44?
Not for hardness. In NSF’s listings, the Hardness Reduction claim appears only under NSF/ANSI 44, the standard for cation exchange softeners, and shower filters certified under NSF/ANSI 177 carry only a chlorine claim. If a salt-free product says it “softens” water, ask which standard and which claim back that up.
As always, check the exact model number on the certifier’s own listing, and find your hardness first: your water quality report for city water, or a test for a well.
Published by the Checked Water editorial team
Related terms
Sources
- NSF Listings: NSF/ANSI 44 Cation Exchange Water Softeners (Source, NSF, 2026)
- NSF Listings: NSF/ANSI 177 Shower Filtration Systems, Aesthetic Effects (Source, NSF, 2026)
- Treatment Devices for Private Well Contaminants (P-03494) (Clinical guideline, Wisconsin Department of Health Services, 2024)
- Home Water Treatment (Clinical guideline, Minnesota Department of Health, 2024)