Nothing, for scale conditioning. No standard at any of the three certifiers covers it.
559 products across the three certifiers carry a hardness claim, and every one holds it under NSF/ANSI 44 — cation exchange, which removes hardness by swapping calcium and magnesium for sodium. That is precisely what a salt-free conditioner does not do; it conditions scale rather than removing hardness.
Something else. Products named for conditioning — antiscalants, ScaleGard — hold NSF/ANSI 42, 53 or 58 listings, which certify taste and odour, health effects, or reverse osmosis performance. None of them certifies scale conditioning.
The absence of a listing is not evidence against a salt-free conditioner. There is no listing to be absent from. Counting that silence against the product would be the same error we made about WQA and NSF/ANSI 401, turned on a manufacturer.
The business plan calls this the most contested category in water and says the honest answer wins it. The honest answer is that the question cannot be settled by certification, and that anyone implying otherwise — in either direction — is overreaching.
How we can say this about a whole category
A claim about every product in a category cannot rest on a search.
Searching for something and not finding it establishes that the
search found nothing, which is a different fact — and we have
published a
retraction
over getting exactly that wrong. So this rests on the complete set
of all three certifiers, enumerated by routes that bypass every
keyword search.
- NSF. Complete listing set per standard via Listings.asp with an empty trade name. 12 requests, 12,086 rows.
- WQA. Complete set by probing standard ids 0-200; 19 answered. 9,205 listings. An earlier pass browsed nine hardcoded ids and missed 3,245 listings including all of NSF/ANSI 401 — see docs/certifier-index-gaps.md.
- IAPMO. Census of certificate ids 1-46,000. 45,999 read, none left unread, 7,395 live certificates, 92,412 model numbers scanned.
Read 2026-09-21. Recorded at
verified_absent, the only strength at
which this site states an absence: every certifier's complete set
enumerated, and the product not in it. Anything weaker is recorded
as a fact about our search rather than about the product.
Corrections are welcome and we will publish them, as we have
before. Contact.