Nitrite in well water

The county where Nitrite is found above the limit most often is Wake County, North Carolina: <1% of 122 private wells tested, according to NCWELL private well summaries.

Nitrite is the short-lived form of nitrogen from septic systems and fertilizer. It causes the same infant blood disorder as nitrate at a tenth of the concentration, and usually points to fresh contamination.

EPA limit: 1 mg/L (EPA MCL as nitrogen (40 CFR 141.62))
North Carolina level: 1 mg/L
CAS number: 14797-65-0

Check your nitrite number

Type the value from your lab report. It is compared to the EPA limit, the same way the full interpretation does it.

Test your own well for nitrite

Certified lab analysis of your own tap water, bottles and prepaid return shipping included. The Essential well panel covers arsenic, uranium, nitrate, lead, copper, manganese, iron, sodium and bacteria; radon and PFAS are add-ons.

Order the Tap Score well water test kit, from $209 Already tested? Upload the report

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Systems that remove nitrite

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For nitrite

Under-sink reverse osmosis system

under-sink or countertop, about $300

Look for NSF/ANSI 58 certification listing the contaminant you need removed.

For nitrite

Aquasana SmartFlow reverse osmosis

under-sink or countertop, about $225

Certified to NSF/ANSI 58 and 53 to reduce arsenic (96%, pentavalent), fluoride (90%), lead (99%), nitrate, nitrite and PFOA/PFOS at the kitchen tap, with a remineralizer.

Rather have it installed and sized for your well? Book a free in-home water test with a licensed local company.

Where nitrite is worst, by homeowner tests

Counties ranked by the share of private wells above the state guidance level in tests homeowners sent to the state lab. Shares combine town summaries, weighted by wells tested.

County	Above state level	Wells tested	Highest
Wake County, North Carolina	<1%	122	1.2 mg/L
Haywood County, North Carolina	<1%	676	1.5 mg/L
Wilson County, North Carolina	<1%	346	1 mg/L
Durham County, North Carolina	<1%	352	1 mg/L
Moore County, North Carolina	<1%	474	1.1 mg/L
Currituck County, North Carolina	<1%	1,014	1 mg/L
Wilkes County, North Carolina	<1%	502	1.6 mg/L
Sampson County, North Carolina	<1%	602	1 mg/L
Lincoln County, North Carolina	<1%	1,276	1 mg/L
Nash County, North Carolina	<1%	1,239	2.1 mg/L
Granville County, North Carolina	<1%	635	1 mg/L
Aroostook County, Maine	<1%	1,089
Sullivan County, New Hampshire	<1%	733	1.8 mg/L
Knox County, Maine	<1%	798
Franklin County, Maine	<1%	938

By individual samples

Counties with at least 30 individual samples in public monitoring data, against the EPA limit.

County	Above EPA limit	Samples	Detected
Monterey County, California	6%	79	25%
Tulare County, California	2%	181	37%
Lewis County, Idaho	2%	52	12%
Minidoka County, Idaho	2%	114	15%
Owyhee County, Idaho	<1%	206	8%
Tehama County, California	<1%	223	<1%
Canyon County, Idaho	<1%	1,262	13%
Franklin County, Idaho	0%	50	28%
Bear Lake County, Idaho	0%	65	17%
Kootenai County, Idaho	0%	110	12%
Custer County, Idaho	0%	64	11%
Valley County, Idaho	0%	93	11%
San Diego County, California	0%	137	10%
Bonneville County, Idaho	0%	120	10%
Adams County, Idaho	0%	52	10%

How to test

Use a state-certified lab and a proper sampling bottle; hardware-store strips cannot measure nitrite at the levels that matter. Collect from the kitchen tap before any treatment, and again after treatment if you install it.

How to treat

Point-of-use reverse osmosis
Anion exchange
Distillation