How to Test for Nitrates in Well Water (And What to Do If Levels Are High)
Well Water Testing
How to Test for Nitrates in Well Water (And What to Do If Levels Are High)
The only way to know if your well water has nitrates is to test. Here's how, how often, and exactly what to do if your levels are high.
For a comprehensive overview of nitrate contamination, health risks, and all treatment options, read our complete nitrate guide. For general well water testing beyond nitrates, see our Complete Guide to Testing Well Water. Already have your test results back? Our How to Read Well Water Test Results guide covers every parameter on your report.
TL;DR: Testing for Nitrates in Well Water
Nitrates are colorless, odorless, and tasteless. The only way to know if they're in your water is to test. Here's what you need to know:
- Test annually at minimum. Every private well should be tested for nitrates at least once per year (EPA recommendation). Test quarterly if you live near farmland or have a septic system.
- Use a certified lab, not just test strips. Lab tests measure the exact concentration in mg/L. Test strips give rough positive/negative results but are not precise enough for health decisions. Our Well Water Test Kit ($199) covers 53 contaminants including nitrates through a certified independent lab.
- The EPA maximum contaminant level (MCL) is 10 mg/L nitrate-nitrogen. At or above this level, the water is unsafe to drink, especially for infants under 6 months.
- If levels are above 10 mg/L: do NOT give the water to infants, and do NOT boil it. Boiling concentrates nitrates. Use bottled water immediately while you arrange treatment.
- Treatment options: A whole house nitrate filter ($2,895) treats all the water in your home. A reverse osmosis system ($595) treats drinking water at one tap. Which one you need depends on your levels and household.
- Not sure what your numbers mean? Call Aidan at 800-460-5810 for a free, no-pressure interpretation of your water test.
Why Test for Nitrates in Well Water?
Nitrates are one of the most common contaminants in private well water, and they're one of the most dangerous because you cannot detect them without testing. Nitrate-contaminated water looks, smells, and tastes exactly like clean water.
This makes nitrates different from most other well water problems. Iron stains your fixtures orange. Sulfur makes your water smell like rotten eggs. Low pH corrodes your pipes. Nitrates do none of these things. A family can drink water with dangerous nitrate levels for years without any visible sign.
Why Nitrates Are a Health Priority
Infants under 6 months are at the highest risk. Nitrates interfere with the blood's ability to carry oxygen, causing a condition called methemoglobinemia (blue baby syndrome). The EPA, CDC, and WHO all classify nitrate contamination as a serious health concern in drinking water. Long-term exposure in adults has been linked to increased risk of certain cancers and thyroid problems, though the evidence is strongest for infant health effects.
The other reason testing matters: nitrate levels fluctuate seasonally. A well that tests safe in winter might exceed safe limits in spring after fertilizer application or heavy rains wash contaminants into the groundwater. One clean test does not guarantee your water stays clean year-round.
The EPA recommends that every private well owner test for nitrates at least once per year. Public water systems are tested regularly and regulated; private wells are entirely the homeowner's responsibility.
How Often to Test for Nitrates
The testing frequency that makes sense for your home depends on your risk factors. Here are the guidelines, based on EPA and state health department recommendations:
| Situation | Recommended Frequency | Why |
|---|---|---|
| Every private well (baseline) | Annually | EPA minimum recommendation for all private wells |
| Near agricultural land or livestock | Quarterly (4x per year) | Fertilizer and manure are the #1 source of nitrate contamination |
| Near a septic system (within 100 feet) | Quarterly | Failing or aging septic systems leach nitrogen into groundwater |
| After heavy rain or flooding | Immediately after | Surface runoff can wash nitrates into shallow wells rapidly |
| Pregnant, nursing, or infant in home | Quarterly | Vulnerable populations face the highest risk from nitrate exposure |
| New well or recently repaired well | Before first use, then quarterly for the first year | New wells need baseline data; repairs can temporarily affect water quality |
| Previous test showed 5+ mg/L | Quarterly | Levels approaching the EPA limit need closer monitoring |
| Shallow well (less than 100 feet deep) | Twice per year (spring and fall) | Shallow wells are more vulnerable to surface contamination |
When to Test During the Year
If you test once per year, the best time is late spring or early summer. This is when nitrate levels typically peak because spring rains wash fertilizers and snowmelt through the soil into groundwater. A spring test catches the worst-case scenario. If you test quarterly, aim for March, June, September, and December to capture seasonal variation.
Testing Methods Compared: Which Nitrate Test Should You Use?
There are three ways to test for nitrates in your drinking water. They vary significantly in accuracy, cost, and usefulness for making treatment decisions.
| Method | Accuracy | Cost | Best For | Limitations |
|---|---|---|---|---|
|
Certified lab test RECOMMENDED |
Highest (±0.1 mg/L) | $20-$40 standalone; included in comprehensive kits | Making treatment decisions, health assessments, baseline testing | Takes 5-10 business days for results; must follow sampling instructions carefully |
| DIY test strips | Low (positive/negative only) | $10-$20 for a pack | Quick screening, peace of mind between lab tests | Cannot give you an exact ppm reading. A strip that says "safe" could be 8 mg/L (approaching the limit). Not sufficient for health decisions. |
| At-home digital meter | Moderate (±2-3 mg/L) | $50-$150 | Monitoring between lab tests, tracking trends over time | Requires calibration. Less precise than lab testing. Good for trending, not for absolute values. |
Our Recommendation: Get a Lab Test First
For nitrates specifically, a certified lab test is the only method accurate enough for health decisions. The difference between 8 mg/L and 12 mg/L is the difference between "monitor" and "treat immediately." Test strips can not distinguish between those two readings.
Our Well Water Test Kit ($199) tests for 53 contaminants including nitrates through an independent certified lab. You get exact concentrations for every parameter, not just pass/fail. One kit covers nitrates, iron, hardness, pH, bacteria, lead, arsenic, and dozens more.
Many state and county health departments also offer free or low-cost nitrate testing for private well owners. Check with your local health department first.
If you already have a lab test, use test strips or a digital meter between lab tests to watch for sudden changes. Think of it this way: the lab test is your annual physical, and the home test is checking your own blood pressure.
Understanding Your Nitrate Test Results
Nitrate results are reported in milligrams per liter (mg/L), which equals parts per million (ppm). There are two ways labs report nitrate:
- Nitrate as nitrogen (NO₃-N): This is the standard used by the EPA. The MCL of 10 mg/L refers to this measurement.
- Nitrate (NO₃): Some labs report total nitrate. The equivalent MCL for total nitrate is 45 mg/L. To convert NO₃ to NO₃-N, divide by 4.43.
Check which format your lab used. Most certified labs report nitrate as nitrogen (NO₃-N), and all the levels in this guide use that standard.
Nitrate Levels: What Your Numbers Mean
The Boiling Mistake
Many people's first instinct when they learn about contamination is to boil the water. Do not boil water to remove nitrates. Unlike bacteria, nitrates are not destroyed by heat. Boiling actually evaporates some of the water while the nitrates stay behind, increasing the concentration. If your water has 12 mg/L of nitrate and you boil off half the water, you now have roughly 24 mg/L. Use bottled water instead.
What to Do If Your Nitrate Levels Are High
If your water test comes back above 10 mg/L nitrate-nitrogen, here is exactly what to do, broken into immediate, short-term, and long-term steps.
Immediate Steps (Today)
- Switch to bottled water for drinking, cooking, and especially for mixing infant formula. Standard water filters (Brita, PUR, refrigerator filters) do NOT remove nitrates.
- Do NOT give the water to infants under 6 months. They are the most vulnerable to nitrate poisoning.
- Do NOT boil the water. Boiling concentrates nitrates and makes the problem worse.
- Pregnant and nursing women should also use bottled water as a precaution.
Short-Term Steps (This Week)
- Retest to confirm. A single test can catch a seasonal spike. Get a second certified lab test to confirm the level is sustained. If you used our Well Water Test Kit the first time, your lab report will give you exact numbers to act on.
- Investigate the contamination source. Check for nearby agricultural activity, fertilizer use on your own lawn, septic system age and distance from the well, and well casing integrity (see the sources section below).
- Talk to your local health department. Many county health departments offer free nitrate testing and can help identify contamination sources.
Long-Term Solution: Treatment
If retesting confirms elevated nitrates, you have two treatment approaches depending on your situation:
| Treatment | What It Does | Best For | Price |
|---|---|---|---|
| Fleck 5600SXT Whole House Nitrate Filter | Ion exchange resin selectively removes nitrates from all water entering your home. Regenerates with salt, similar to a water softener. | Homes with sustained levels above 10 mg/L where you want every tap protected. Families with infants or pregnant women. Homes where multiple people drink the tap water. | $2,895 |
| Pure-75 Reverse Osmosis System | Membrane filtration removes nitrates (along with most other dissolved contaminants) from drinking water at a single tap, typically under the kitchen sink. | Homes with moderate levels (10-15 mg/L) where you primarily need safe drinking and cooking water. Also works as a complement to whole house treatment. | $595 |
Which one do you need? For most homes with levels between 10 and 15 mg/L, an under-sink reverse osmosis system is a practical, affordable first step. It protects the water you actually drink and cook with. For higher levels, families with vulnerable members, or homeowners who want every tap treated, the whole house nitrate filter is the comprehensive solution. Ready to compare nitrate removal systems side by side? See our Best Nitrate Filter for Well Water buyer's guide. For annual costs, resin life, and long-term cost of ownership, see our Nitrate Filter Cost & Maintenance guide.
Not sure which approach is right for your situation? Call Aidan at 800-460-5810 with your water test results. Aidan sizes nitrate systems based on your actual water chemistry, household size, and water usage. Free, no-pressure guidance.
What About Standard Carbon Filters?
Standard carbon filters (Brita, PUR, fridge filters, whole house carbon) do not remove nitrates. Neither do water softeners, sediment filters, or UV systems. Nitrate removal requires either ion exchange with nitrate-selective resin (whole house filter) or reverse osmosis (point of use). This is one of the most common misconceptions we hear from homeowners. If you already have a whole house filtration setup, you may still need a separate nitrate-specific system. See our Complete Guide to Well Water Filtration Systems for how nitrate treatment fits into a full treatment sequence.
Where Nitrates Come From: Investigating Your Contamination Source
If your well water tests positive for nitrates, identifying the source helps you understand whether the problem is fixable at its origin or if you'll need ongoing treatment. Here are the most common sources:
Agricultural Runoff
The #1 source of nitrate contamination in private wells nationwide. Nitrogen-based fertilizers applied to cropland dissolve in rain and irrigation water, then migrate downward into the water table. Livestock operations (especially concentrated animal feeding operations) produce nitrogen-rich manure that leaches into groundwater. If your property is near active farmland, this is the most likely culprit.
Septic Systems
Septic systems discharge nitrogen as part of normal operation. A properly functioning septic system 100+ feet from your well usually isn't a problem. But aging, failing, or undersized septic systems (yours or a neighbor's) can introduce significant nitrate contamination. If your septic system is more than 20-25 years old or within 75 feet of your well, this is worth investigating.
Lawn Fertilizer
Residential fertilizer is a commonly overlooked source. If you or your neighbors fertilize lawns heavily, the nitrogen that isn't absorbed by grass roots eventually reaches the water table. This is especially relevant for shallow wells (under 100 feet).
Well Construction and Casing
A poorly constructed, old, or damaged well casing allows surface water to channel directly into your well without being filtered through soil. This is the easiest source to fix: a well contractor can inspect and repair the casing, replace a damaged well cap, or improve the surface seal. Shallow wells with short casings are particularly vulnerable.
Natural Geological Sources
In some regions, naturally occurring nitrogen in geological deposits can contribute to background nitrate levels. This is less common than human-caused contamination but does occur in certain formations. If your area has no obvious agricultural or septic source, geological testing may be warranted.
Identifying and addressing the source (where possible) is the best long-term strategy. A well that's contaminated by a cracked casing can be repaired. But if the source is regional agricultural runoff, treatment is the only practical solution.
For help investigating your specific situation, read our Well Water Problems guide, which covers how to diagnose contamination sources for every common contaminant.
Frequently Asked Questions
How do I test my well water for nitrates?
The most reliable way is a certified lab test. Collect a sample following the lab's instructions (usually a clean container, no air bubbles, delivered or mailed within 24-48 hours) and submit it for analysis. Our Well Water Test Kit ($199) includes nitrate testing along with 52 other contaminants. You can also contact your county health department, as many offer free or low-cost nitrate testing for private well owners.
How do you know if your well water has nitrates?
You cannot tell without testing. Nitrates are colorless, odorless, and tasteless. There is no visual sign, no smell, and no taste change at any concentration. The only way to know is to test the water with a certified lab or a home test kit. This is what makes nitrates particularly dangerous compared to contaminants like iron (visible staining) or sulfur (rotten egg smell).
How do I fix high nitrates in my well water?
Two proven treatment methods remove nitrates: ion exchange (whole house filter with nitrate-selective resin) and reverse osmosis (point-of-use membrane system). A whole house nitrate filter ($2,895) treats all the water in your home. An under-sink reverse osmosis system ($595) treats drinking water at one tap. Standard carbon filters, water softeners, and boiling do not remove nitrates. Call Aidan at 800-460-5810 with your test results for a specific recommendation.
How often should you test well water for nitrates?
The EPA recommends at least once per year for all private wells. Test quarterly if you live near agricultural land, have a septic system within 100 feet, have infants or pregnant women in the home, or if a previous test showed levels above 5 mg/L. The best time for an annual test is late spring or early summer, when nitrate levels typically peak.
Can I smell or taste nitrates in my water?
No. Nitrates have no odor, no color, and no taste at any concentration found in groundwater. You could drink water with 50 mg/L of nitrate and not notice anything different. This is precisely why testing is the only way to protect your family. Do not rely on your senses to detect nitrate contamination.
Do nitrate levels change throughout the year?
Yes, often significantly. Nitrate levels in well water typically peak in spring and early summer when rain and snowmelt wash fertilizers through the soil into the water table. Levels may drop in late summer and winter when less nitrogen is being applied and less water is moving through the soil. This is why a single test isn't always representative. If you get a borderline result (5-10 mg/L), test again in a different season to understand the full range.
Can I use a home test strip to decide if I need treatment?
Test strips are useful for quick screening, but they are not accurate enough for treatment decisions. Most nitrate test strips show color changes in broad ranges (0, 10, 25, 50 mg/L). They cannot tell you the difference between 6 mg/L (monitor) and 12 mg/L (treat immediately). For any result that isn't clearly zero, follow up with a certified lab test before making treatment decisions. Use strips between lab tests for trend monitoring.
Should I test for nitrites too?
Yes. Most certified lab tests include both nitrate (NO₃) and nitrite (NO₂). Nitrite is a related compound that converts to nitrate in the environment. The EPA MCL for nitrite is 1 mg/L, much lower than the nitrate limit. Nitrite is actually more toxic than nitrate at equivalent concentrations. Some labs report "nitrate + nitrite" as a combined value with an MCL of 10 mg/L. Our Well Water Test Kit includes both.
What is "blue baby syndrome"?
Methemoglobinemia (blue baby syndrome) occurs when nitrates in drinking water interfere with an infant's hemoglobin, reducing the blood's ability to carry oxygen. Affected infants may develop a bluish skin color, especially around the lips and fingertips, and may become lethargic or have difficulty breathing. It primarily affects infants under 6 months because their digestive systems more readily convert nitrate to nitrite, and their hemoglobin (fetal hemoglobin) is more susceptible. This is why the EPA MCL of 10 mg/L exists, and why infants should never consume water exceeding this level.
Does a reverse osmosis system remove nitrates?
Yes. Reverse osmosis is one of the two proven methods for removing nitrates from drinking water. A quality RO system removes 83-92% of nitrates along with most other dissolved contaminants. The Pure-75 RO system ($595) installs under your kitchen sink and provides nitrate-free drinking and cooking water. For whole-house protection, a dedicated nitrate filter is the better option. For more on reverse osmosis for well water, see our Reverse Osmosis for Well Water guide.
Nitrate Guides from Mid Atlantic Water
- Nitrates in Well Water: Health Risks, Safe Levels & How to Remove Them
- Best Nitrate Filter for Well Water -- whole-house and under-sink options compared
- Nitrate Filter Cost & Maintenance -- resin life, regeneration costs, and 10-year total cost of ownership
About the Expert: Aidan Walsh
With over 30 years of hands-on experience in water treatment, Aidan serves as the lead technical expert at Mid Atlantic Water. He specializes in diagnosing and designing whole-home water treatment solutions for residential wells, including nitrate contamination. Aidan reviews hundreds of water tests every month and personally recommends treatment configurations based on each home's specific water chemistry, contamination sources, and household needs.