Contaminant

Nitrate in drinking water

Also listed as Nitrate-N · Nitrate as nitrogen · Nitrate nitrogen

From fertilizer and septic runoff. A serious risk for infants (“blue-baby syndrome”).

This page can’t tell you what’s in your tap water.

Only a test of water from your own tap can. Public-system results describe the system, not your home.

01Check your water systemWater Check · system results, not your tap 02Test your tapHow to get a reliable result 03Treatment approachesWhat can reduce it at the tap

On this page · 10 sections

01Reference values
02Is it in my water?
03Where it comes from
04Testing
05Water filters
06Treatment
07Evidence
08Next steps
09Ask about nitrate
10References

Reference values

An enforceable limit for public water systems.

Each value says what kind of reference it is, and they mean different things. A lower or missing number never means water is safe.

Enforceable limit · MCLFederal · public water systems

10 ppm

The highest level allowed in water a public system delivers. A legal limit, not a health goal.

Applies to: Water delivered by public water systems, not private wells
Status: In force
Source: EPA NPDWR MCL (10 mg/L as N) · 40 CFR §141.62

Health-based goal · MCLGFederal · not enforceable

10 ppm

The level below which no known health risk is expected. A goal, not a limit.

Applies to: Set alongside the rule as a public-health goal
Status: Published goal
Source: EPA National Primary Drinking Water Regulations — MCLG 10 mg/L · 40 CFR §141.51

Check your result’s basis

Says “as N”

Comparable to a reference stated as nitrogen.

Says “as NO₃”

A different, larger scale. Don’t compare directly.

Doesn’t say

We won’t compare it to any number. Ask your lab which basis they used.

Your stateNot held yetStates may set their own references. We don’t hold a state reference for nitrate yet.

Is it in my water?

Only a test of your own tap can tell.

Choose what you have. We’ll show what it can and can’t tell you.

If you haven’t tested

Nobody can tell without a measurement, including us.

Three things you can do, in this order.

Test water from your tapThis is the only way to know your level. Testing guidance ↓See what your system reportsSystem results aren’t a tap measurement. Open Water Check →On a private well?Public-system reports don’t cover wells. Open Well Water →

Where it comes from

Agricultural runoff and nitrogen-based fertilizers
Contaminated private drinking water wells
Well water in areas with inadequate well construction or casing

Why it matters

Nitrate in drinking water above 10 milligrams per liter can cause methemoglobinemia in infants less than six months old, a potentially fatal condition in which hemoglobin loses its ability to carry oxygen, leading to gray-blue discoloration of skin, elevated heart rate, weakness, nausea, and in severe cases death.

Emerging evidence indicates potential associations between nitrate exposure and health effects in adults including increased heart rate, nausea, headaches, and abdominal cramps.

Testing

How to test your tap water for nitrate

Nitrate concentration in drinking water can be measured through laboratory water testing of a sample from your tap.

01Use a certified labA state-certified lab, or a kit that sends samples to one.
02Follow the sampling stepsHow and when you collect the water changes the result.
03Check the reportIt should state units and the detection limit.

Certified labNot sponsored

Use a state-certified labYour state keeps a list of labs certified for drinking water.

Choosing a filter for nitrate

None qualify

No products currently qualify for a nitrate pick here.

Nothing in our database has a nitrate claim for an exact configuration we can verify.

Find a fit in Finder Read treatment approaches

Treatment

How to reduce nitrate in water

Function: ReduceStandard carbon filters don’t reduce nitrate. It takes a membrane, ion exchange or distillation.

Reverse osmosisReverse osmosis forces water under high pressure through a semi-permeable membrane that physically removes nitrate and other inorganic contaminants, though this process generates a concentrated reject stream that requires disposal.Before you chooseClaims apply to the exact model and configuration tested.

Ion exchangeAnion exchange uses a synthetic resin bed to exchange nitrate ions with less harmful chloride ions, achieving high removal efficiencies; the resin can be regenerated or replaced, and spent regenerant requires disposal.Before you chooseClaims apply to the exact model and configuration tested.

DistillationThe water is boiled into steam and condensed, which leaves nitrate behind. Boiling water on its own doesn’t reduce nitrate and can concentrate it.Before you chooseClaims apply to the exact model and configuration tested.

Whole-house systems and point-of-use filters treat different water. A whole-house system treats water where it enters the home; a point-of-use filter treats the tap it’s installed on. Check which one a claim is for.

Evidence

What the evidence means

We keep evidence types apart. A result for one configuration never stands in for another, and we never average across types.

No product in our database holds a reduction record for nitrate yet.

How we read evidence →

Next steps

Take the next step

Match a system to your homeFinder asks about your home first. It suggests nitrate as a starting point, and nothing counts until you confirm it.

Ask about nitrate

Still have a question?

Answers come only from WaterDecoder’s reviewed sources and show citations. Ask can’t interpret your test result or choose a product. Don’t include personal details.

AI assistant

Ask about Nitrate

Answers draw on cited public-health sources and the filters certified to reduce Nitrate. Every source is linked, and if the sources don’t cover a question, the answer says so.

Questions to start with

Educational information from cited sources. Not medical or professional advice.

References

Where these facts come from

Written and maintained by WaterDecoder. A review date appears only once we have confirmed one.