Nitrate
A genuine health parameter with a hard regulatory limit, and the one that matters most for infants.
- Safe range
- 0 – 10 mg/L (US EPA limit)
- Ideal range
- 0 – 5 mg/L
- Measured in
- mg/L
What it is
Nitrate enters groundwater from fertiliser, septic systems and animal waste. It is colourless, odourless and tasteless, so there is no way to detect it without a test, which is precisely why it deserves attention rather than assumption.
Why it matters
This is not a taste or appliance question. High nitrate interferes with the blood's ability to carry oxygen, and infants under six months are dramatically more vulnerable than adults; the condition is methaemoglobinaemia, historically called blue baby syndrome. The US EPA maximum contaminant level is 10 mg/L (measured as nitrate-nitrogen), and it is health-based. Private wells near agricultural land are the classic risk case, and they are not tested by anyone unless the owner arranges it.
How to measure it
If you are on a private well, this is the test to do, and to do on a schedule. Nitrate is one of the few parameters where strips are genuinely useful for screening, and any result approaching the limit should be confirmed by a laboratory.
Certified laboratory, mail-in kit
- How trustworthy
- Reference grade
- Cost
- Most expensive
- Effort
- Careful sampling, then days or weeks of waiting
You are posted bottles and instructions, you fill them exactly as told, and you post them back. Weeks later a report arrives with figures nobody has to interpret by eye. This is what a result you intend to act on should be built from.
A standard well panel covers nitrate and nitrite alongside bacteria. This is the result to act on, and the one to have in hand before an infant is drinking the water.
Where to find it: State-certified drinking water laboratories; your state's certification officer keeps the list, and many public health departments will point you at one.
Test strips
- How trustworthy
- Dependable
- Cost
- Low cost
- Effort
- Under a minute, wherever you drew the sample
A plastic strip with reagent pads on it. Dip it, hold it level, and match each pad against the chart on the bottle at the time the label tells you to. Most strips read several parameters at once.
A dip, a wait, and two pads reading nitrate and nitrite. As a screen between laboratory tests on a well near farmland, strips are worth their price.
Watch out: Strips usually report nitrate as NO3, while the regulatory limit is written as nitrate-nitrogen, NO3-N. They are different numbers for the same water. Check which one the bottle reports before comparing it with the limit.
Where to find it: Pool shops, hardware stores, supermarkets and online, sold both per parameter and as multi-packs. Buy strips made for your kind of water: pool strips and drinking water strips read very different scales for the same chemistry.
Your utility's annual water quality report
- How trustworthy
- Reference grade
- Cost
- Free
- Effort
- A few minutes of reading
Every community water system in the US has to publish one each year, free, listing what it found and what the limits are. It is real laboratory data about the water leaving the plant and travelling the mains. What it cannot describe is your own plumbing.
Public systems test for nitrate frequently and publish the range. If you are on a mains supply, this is generally the whole answer.
Where to find it: Your water bill, your supplier's website, or the EPA's index of reports. It is also called a Consumer Confidence Report or CCR.
Taking the sample
For several of these the sample is where the error is, and no instrument recovers from a bad one.
- • Test at least annually on a private well, and again after heavy rain, after spring melt, and after any work on a nearby septic system. Nitrate arrives with water moving through soil, so it spikes with weather rather than drifting slowly.
- • Sample from the tap you actually drink from, and take it before any treatment if you want to know what the well is doing.
Further reading: US EPA: private drinking water wells, including what to test for and when; US EPA: certified drinking water laboratories, by state
If it is too low
Low or undetectable nitrate. Nothing to act on.
- • No action needed. Retest periodically if you are on a private well.
If it is too high
Above 10 mg/L the water is not considered safe to drink, and is specifically unsafe for infants under six months and during pregnancy. Boiling does not help; it concentrates nitrate rather than removing it.
- • Do not use the water for infant formula, and do not boil it; boiling concentrates nitrate.
- • Confirm with a certified laboratory test before acting on a home result.
- • Reverse osmosis, ion exchange or distillation remove nitrate. Standard carbon filters do not.
- • If you are on a private well near farmland or a septic system, treat this as a regular test rather than a one-off.
Common questions
What is the safe level of nitrate in drinking water?
The US EPA maximum contaminant level is 10 mg/L as nitrate-nitrogen. This is a health-based limit rather than an aesthetic guideline, and it is set specifically to protect infants, who are far more susceptible than adults.
Does boiling water remove nitrate?
No, it makes it worse. Boiling evaporates water and leaves the nitrate behind, so the concentration rises. Removing nitrate requires reverse osmosis, ion exchange or distillation.
Can I taste or smell high nitrate?
No. Nitrate is colourless, odourless and tasteless at any concentration you would encounter. Testing is the only way to know, which is why well owners near agricultural land are advised to test on a schedule.
WiseWaterGauge helps you record and understand your own readings. It is not a substitute for a certified laboratory test, and nothing here is medical or regulatory advice. If a health parameter is out of range, confirm it with an accredited lab and speak to your water provider.