The narrowest claim, and why that makes it the useful one
NSF’s listing on 2026-09-10, for the NSF/ANSI 58 nitrate/nitrite reduction claim:
| Nitrate, NSF/ANSI 58 | |
|---|---|
| Rows NSF returned | 84 |
| Distinct model designations | 84 |
| Companies | 28 |
| Product categories | 1 |
Every certified model is plumbed-in to a separate tap — under-sink reverse osmosis, on its own faucet.
Eighty-four is a small population, and that is the point of the next section rather than a problem with it.
The four claims nest
Reading all four NSF/ANSI 58 claim sets on the same date:
| Claim | Models | Relationship |
|---|---|---|
| Fluoride reduction | 127 | The outer set |
| Lead reduction | 127 | The same 127 models |
| Hexavalent chromium reduction | 120 | All inside the 127 |
| Nitrate/nitrite reduction | 84 | All inside the 120 |
Not overlapping — strictly nested. Every model holding the nitrate claim also holds hexavalent chromium, fluoride and lead. None holds nitrate without them.
Which gives a clean shortcut. Search the nitrate claim and you are looking at the most capable subset of the under-sink reverse osmosis market, with the other three claims already included.
→ Chromium-6, the next claim out → Filters certified for fluoride, the outer set
If nitrate is not your concern, this is still the sharpest single filter to apply when comparing reverse osmosis systems.
Two things to know before you buy
Both matter more than the product choice, and neither is in any listing.
Boiling makes it worse. Minnesota Department of Health states boiling water does not remove nitrate and makes it more concentrated. The water leaves as steam; the nitrate stays. That instinct is the wrong one here, and it is worth holding firmly during any boil water notice, which is issued for microbial reasons and does nothing for nitrate.
Infants are the group at risk. MDH identifies bottle-fed babies under six months as at highest risk of methemoglobinemia, which can result in serious illness. If that describes your household, this is a now decision rather than a shopping decision.
→ Nitrate: the risk, the units, and where it comes from
The number, and which unit it is in
EPA’s Maximum Contaminant Level is 10 mg/L as nitrate-N, legally enforceable.
Reports express nitrate two ways — 10 mg/L as nitrate-N, or 45 mg/L as nitrate — and the same water reads safe or unsafe depending only on which convention the laboratory used. Check the unit before the number.
→ How to read your water quality report
A limit of this method, stated plainly
EPA maps nitrate to distillation, reverse osmosis or ion exchange.
Only one of those three appears here, and the reason is how NSF indexes claims rather than what works. NSF lists NSF/ANSI 62 as its distillation standard but offers no selectable reduction claims under it, so a search by claim cannot return a distiller — not for nitrate, and not on any other roster on this site.
Ion exchange sits under NSF/ANSI 44, whose four claims are hardness, barium, radium and efficiency, with no nitrate claim among them.
So read “84 certified models” as 84 reachable through this route. A distillation system may well reduce nitrate; it cannot be found this way.
→ Which claims exist at all, and how populated each is
The decision framework
1. Establish the figure and the unit
If nitrate is above 10 mg/L as nitrate-N, and especially if an infant drinks the water, act rather than shop.
If it is below, the remaining question is whether you want reverse osmosis for other reasons — in which case the nitrate claim is a useful filter anyway.
2. Accept the format
Every certified model is under-sink reverse osmosis on a separate tap. If that does not fit your home, no certified alternative appears in this listing, and the honest next step is asking a supplier which body certified their alternative and for which claim.
→ How to read an NSF listing, footnotes included
3. Use the nesting rather than fighting it
Filter on nitrate. You get the narrowest, most capable set, and hexavalent chromium, fluoride and lead arrive with it.
4. Confirm the claim on the model
Under NSF/ANSI 58, TDS reduction is the only required claim. Everything else, nitrate included, is optional and listed per model.
Applying the framework: who holds the claim
| Company | Models |
|---|---|
| Microline | 14 |
| EcoWater Systems LLC | 9 |
| The LeverEdge | 8 |
| Water Channel Partners | 8 |
| Hellenbrand Inc. | 6 |
| Aqua Systems | 4 |
| Lancaster Water Treatment | 4 |
| GE Appliances | 3 |
| Senwater Systems LLC | 3 |
The remaining 19 companies hold two or fewer models each.
Notes tied back to the criteria
- The holder list is a shortened version of the fluoride and chromium lists, which follows from the nesting rather than being a separate finding.
- Most are dealer-channel water treatment firms — Hellenbrand, Lancaster, The LeverEdge, EcoWater — so buying one usually means a dealer rather than a shelf.
- GE Appliances is the one broadly retail name in the top group, at three models.
- Nothing here separates the 84 on performance. NSF records claim membership and no reduction percentage.
The decision path
| Your situation | What decides it | Where that lands you |
|---|---|---|
| Nitrate above 10 mg/L, infant in the house | Acute risk | Act now; alternate water meanwhile |
| Nitrate above the limit, no infant | The figure | Under-sink RO, 84 models |
| Below the limit, want RO anyway | The nesting | Filter on nitrate for the capable subset |
| Tempted to boil | Boiling concentrates it | Do not; it makes the figure worse |
| Want a pitcher | No claim exists under 42 or 53 | No certified option |
| Considering a distiller | NSF 62 has no searchable claims | Ask the maker which body certified it |
| No figure yet | Nothing to size | Annual report, or a test |
Choose an under-sink reverse osmosis system if
- You need a certified nitrate claim. It exists in no other format here.
- You want hexavalent chromium, fluoride and lead on the same unit, which all 84 models hold.
- You accept the running cost. EPA notes reverse osmosis uses approximately three times as much water as it treats.
Choose alternate water first if
- An infant under six months is bottle-fed on water above the limit. Equipment takes time to fit; the exposure does not wait.
Choose to buy nothing if
- Your figure is well below 10 mg/L as nitrate-N and you have no other reason to fit reverse osmosis.
Mistakes that cost the most money
Boiling. The most dangerous mistake on this page, because it feels protective and concentrates the contaminant instead.
Reading the wrong unit. 10 mg/L as nitrate-N and 45 mg/L as nitrate describe the same water. Compare like with like before concluding anything.
Buying a pitcher or carbon block. No nitrate claim exists under NSF/ANSI 42 or 53, so no such product can be certified for it.
Assuming any reverse osmosis system covers nitrate. Only TDS reduction is required under NSF/ANSI 58. Forty-three of the 127 fluoride-certified models do not hold the nitrate claim.
Treating a distiller’s absence here as a verdict. NSF offers no selectable claims under its distillation standard, so the search cannot reach them.
Forgetting membrane replacement. A certified claim describes a unit inside its rated service life.
Three situations, and what changes
A bottle-fed infant and a figure above the limit. The one case where equipment is the second decision. Use an alternate water source for formula immediately, then fit treatment.
Agricultural area, well or small municipal supply, figure creeping up. Annual testing is what MDH recommends, and a rising trend is more informative than a single reading. Fit before it crosses rather than after.
You are already shopping for reverse osmosis for fluoride or lead. Filter on nitrate anyway. It costs nothing to apply, narrows 127 models to 84, and every one of those 84 holds all four claims.
The objections worth answering
“Only 84 models?” For one claim under one standard in one certifier’s listing, yes. It is also the narrowest of four nested claims, so those 84 are the most broadly certified systems in that market rather than a fringe.
“My filter says it reduces nitrate.” Then ask which accredited body certified that claim, and under which standard. If the product is certified to NSF/ANSI 42 or 53, no nitrate claim exists there to hold.
“Reverse osmosis wastes water.” It does — EPA puts it at roughly three times as much water used as treated. That is a real cost to weigh, and it is why these systems sit at one tap rather than treating a house.
“These figures will move.” They will. NSF dates its listings and asks readers to confirm status at source, which is why the capture date sits beside every figure here.
Who this is for
Anyone with nitrate on a report deciding what to fit, and anyone comparing reverse osmosis systems who wants a single sharp filter to apply.
It is not the contaminant page. The risk, the sources and the testing schedule live there, and anyone with an infant in the house should start there.
What to settle first
What is my figure, in which unit, and is there an infant drinking this water?
Those three answers decide whether this is a purchase or an emergency. The product choice is the easy part afterwards.
→ Nitrate: the risk, the units, and where it comes from → Chromium-6, the next claim out in the same standard → Which claims exist at all, and how populated each is → Arsenic, where the NSF/ANSI 58 claims do not nest → Boil water notices, where the standard advice is wrong for nitrate → Reverse osmosis, and the 84 models that hold the nitrate claim → Nitrate on city water: the one chemical limit with a 24-hour notice