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NSF/ANSI 44: Water softeners

Official title: Residential Cation Exchange Water Softeners

Covers home water softeners that trade calcium and magnesium for sodium or potassium. A certified softener was tested for hardness reduction and may hold a few extra claims.

What it can cover

  • Hardness from calcium and magnesium (listing claim: "Hardness Reduction")
  • Barium (listing claim: "Barium Reduction")
  • Radium 226/228 (listing claim: "Radium 226/228 Reduction")
  • Salt and water efficiency (listing term: "Efficiency Rated")

What it does not

  • Lead, PFAS, chlorine taste or other filter claims
  • Bacteria, viruses or cysts
  • Anti-scale devices that do not use cation exchange resin. NSF/ANSI 44 covers only softeners regenerated with sodium or potassium chloride.

The usual mistake

Treating a softener as a drinking water filter. A 44 certification says nothing about lead, PFAS or chlorine. Those need their own claims under other standards.

The fine print

  • Softening swaps hardness minerals for sodium or potassium ions, depending on the salt used.
  • WQA notes that NSF/ANSI 44 defines soft water as less than 1 grain per gallon of hardness (17.1 mg/L).
  • WQA listings word the claim as "Hardness." Both NSF and WQA list certified softeners.

Claims to look for

ContaminantClaim on the listing
HardnessHardness ReductionNSF listing wording for water softeners. WQA wording: "Hardness."

Filters TapBuff has checked against a listing

Every certification below links to the certifier’s own listing. A filter appears here only if its listing shows NSF/ANSI 44.

TapBuff earns a commission if you buy through some links on this page. It does not change which standard or filter we name. As an Amazon Associate, TapBuff earns from qualifying purchases. How TapBuff makes money

  • Aquasana SimplySoft 40,000 Grain Softener (WH-SF40)

    Whole house

    • IAPMO listing: 44 · checked Oct. 4, 2026
    Price on Amazon Maker’s page

  • A.O. Smith 40,000-Grain Water Softener (AO-WH-SOFT-400T)

    Whole house

    • NSF listing: 44 · checked Oct. 4, 2026
    Maker’s page

Sources

  1. NSF Standards for Water Treatment Systems, NSF. Checked Oct. 4, 2026.
  2. NSF/ANSI 44 Technical Requirements, NSF. Checked Oct. 4, 2026.
  3. NSF/ANSI 44-2022: Residential Cation Exchange Water Softeners uploaded (NSF standards workspace), NSF. Checked Oct. 4, 2026.
  4. Search for NSF Certified Drinking Water Treatment Units (standards and reduction claims lists), NSF. Checked Oct. 4, 2026.
  5. Scale Deposits, Water Quality Association. Checked Oct. 4, 2026.
  6. Find WQA Certified Products (Gold Seal listings by standard and claim), Water Quality Association. Checked Oct. 4, 2026.