Nitrite is the less common half of the nitrate and nitrite pair, and finding it in a household supply is more alarming than finding nitrate. Nitrate is widespread from fertilizer and septic influence, while nitrite usually indicates recent contamination or active bacterial conversion somewhere close to the tap. The EPA sets federal limits for both in public water systems.
Nitrite is a signal, not just a number
In an aerated, healthy well, nitrogen ends up mostly as nitrate. Nitrite appears where oxygen is short and bacteria are converting nitrogen compounds, which points at contamination that is recent or close by: a failing septic system, animal waste, a leaking sewer line, or bacterial growth inside the well or the plumbing. That is why a nitrite result normally comes with a recommendation to test for coliform bacteria at the same time.
Who it matters most to
Nitrite is the classic infant risk in drinking water, because it interferes with the blood's ability to carry oxygen and infants under six months are most vulnerable. Pregnant women are also advised to avoid elevated nitrite and nitrate. Crucially, boiling makes it worse rather than better: water leaves as steam and nitrite stays behind, so the remaining water is more concentrated. Use an alternative supply until treatment is confirmed to be working.
Wells are the household's own responsibility
The EPA points out that private wells are not federally regulated under the Safe Drinking Water Act, so no agency tests them and no report arrives. It also cites a USGS study of 2,100 private wells that found about one in five carried at least one contaminant above a human health benchmark. Around 15 percent of the US population, over 43 million people in more than 23 million households, relies on private wells, and nitrate and nitrite testing belongs on their annual list.
What actually removes it
Nitrite is dissolved and carries a charge, so carbon filters, sediment filters and standard softeners do nothing. Reverse osmosis at the sink is the usual household answer for drinking and cooking water. Anion exchange, using a resin dedicated to nitrate and nitrite rather than hardness, treats larger volumes. Distillation also works. Where bacteria are also present, disinfection and finding the contamination path come first, as our well water testing guidance explains.
Questions people ask about nitrite in water
Does boiling remove nitrite from water?
No, it concentrates it. Water leaves as steam while nitrite remains, so boiled water carries more nitrite per glass than it started with.
Will a water softener remove nitrite?
No. A standard softener exchanges hardness ions only. Nitrite needs reverse osmosis, dedicated anion exchange resin, or distillation.
Why test for bacteria if nitrite is found?
Nitrite often signals recent contamination or bacterial activity, so a coliform test helps identify whether waste or surface water is reaching the well.