Well water in Grant County, Washington

1in4

Testing strongly recommended

tested well samples in Grant County exceeded the EPA limit for nitrate (10 mg/L), based on public data from USGS Water Quality Portal.

4,622 test results across 15 contaminants from at least 335 wells, 1916 to 2025; nitrate has the most at 897. Data refreshed September 15, 2026.

Compiled by Nick at Well Water Nerd from public records. How these pages are built

An estimated 30,622 people in Grant County get their drinking water from a private well, per USGS 2015 county water use. That is about 33% of residents.

Separately, the USGS national arsenic model estimates that 13% of the 30,622 people on private wells in Grant County draw water above 10 ug/L (the model's range is 11% to 16%), from geology and well depth rather than local tests.

What individual samples found

Each row summarizes every public sample for that contaminant inside Grant County. Above limit means above the EPA maximum contaminant level; where EPA has no enforceable limit, the row shows a health guideline or nuisance level instead.

Contaminant	Above limit	Samples	Detected	Median	Highest	Limit
Nitrate 1916 to 2025	26%	897	96%	3.61	390	10 mg/L EPA limit
Arsenic 1983 to 2025	25%	143	98%	4.9	116	10 ug/L EPA limit
PFOS 2023 to 2024	9%	23	22%	0	7.8	4 ng/L EPA limit
Uranium 2002 to 2025	4%	134	99%	4.8	47.9	30 ug/L EPA limit
Fluoride 1939 to 2025	0%	552	100%	0.5	3.1	4 mg/L EPA limit
Copper 1970 to 2025	0%	154	65%	0.001	0.038	1.3 mg/L EPA limit
Lead 1970 to 2025	0%	154	50%	0	1.96	15 ug/L EPA limit
Radium (226 + 228) 2004 to 2016	0%	34	38%	0	0.45	5 pCi/L EPA limit
E. coli 2002 to 2016	0%	27	0%	0	0	0 MPN/100mL EPA limit
PFOA 2023 to 2024	0%	23	13%	0	3.6	4 ng/L EPA limit
Chloride 1916 to 2025	no limit	776	100%	12	900	250 mg/L nuisance level
Sodium 1936 to 2025	no limit	691	100%	30	1,120	20 mg/L health guideline
Iron 1916 to 2025	no limit	541	68%	9.3	1,900	300 ug/L nuisance level
Manganese 1961 to 2025	no limit	400	47%	0	160	300 ug/L health guideline
Radon 1993 to 2016	no limit	73	100%	390	1,700	2,000 pCi/L health guideline

Over time

Share of samples above the limit by period. A cell needs ten samples to show; a comparison needs twenty in each period. Later periods sample fewer wells, and often the ones already known to have a problem.

Contaminant	before 2000	2000s	2010s	2020s
Nitrate	21%592 samples	40%112 samples	32%102 samples	32%91 samples
Fluoride	0%414 samples	0%56 samples	0%51 samples	0%31 samples
Copper	0%20 samples	0%52 samples	0%51 samples	0%31 samples
Lead	0%20 samples	0%52 samples	0%51 samples	0%31 samples
Arsenic	n/a	29%52 samples	20%51 samples	29%31 samples
Uranium	n/a	2%52 samples	4%51 samples	6%31 samples

Arsenic above the limit in Grant County rose from 20% of 51 samples in the 2010s to 29% of 31 in the 2020s.

Nitrate, fluoride, copper, lead, uranium have held within a few points between the two most recent periods with enough samples.

Closer than the county

See the sampled wells near your address

The same records, drawn around one point: which wells within a few miles were sampled and what they found, how deep the wells next to you were drilled, and any leaking tank or cleanup site within a mile.

Check my address

What this means

The contaminants most often above their limit here are nitrate (26% of 897 samples), arsenic (25% of 143 samples), and pfos (9% of 23 samples). A well next door can differ sharply from yours because bedrock fractures, well depth and plumbing all matter, so these rates describe the area, not your tap.

Chloride and Iron are widespread in local groundwater. They are mainly a staining and taste problem, but high manganese also carries a health advisory for infants.

What to test for in Grant County

1
Nitrate
26% of 897 local samples were above the limit.
2
Arsenic
25% of 143 local samples were above the limit.
3
PFOS
9% of 23 local samples were above the limit.
4
Uranium
4% of 134 local samples were above the limit.
5
Coliform bacteria
Recommended for every private well, every year.
6
Radon
Median local reading is 390 pCi/L.
7
Fluoride
Detected in 100% of local samples.
8
Volatile organic compounds (VOCs)
7 reported spills and releases on record locally.

Test your Grant County well for nitrate, arsenic and PFOS

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

Just want bacteria checked first? Tap Score coliform and E. coli test, $99. Coliform and E. coli are the tests every well needs every year.

Want a quick look before paying for a lab? Home well water test strips on Amazon check hardness, iron, pH and nitrate in minutes. They are a screen, not a result: arsenic, bacteria, uranium and PFAS need a certified lab.

Affiliate links: the merchant pays us a commission and the price is the same for you. It does not change what the data above says. As an Amazon Associate we earn from qualifying purchases.

Where to get a well tested in Washington: certified labs, state programs and prices.

Already have results back? Get your lab report read against the Grant County numbers, $29. Every line explained, ranked by what matters, with the fix for each.

Wells in Grant County

5,486 domestic wells in Grant County are on record with the state since 1991. the typical well is 180 feet deep (one in ten goes past 425 feet).

In a typical Grant County well, the median yield is 40 gallons per minute.

1,697

1990s

1,499

2000s

1,249

2010s

1,028

2020s

Find your own well's report

The state keeps the driller's report for most wells drilled since 1984. It tells you how deep your well is, where bedrock starts, and how much water it makes, which decides what treatment can work.

Open Ecology well report search and choose Water Well.
It lists depth, casing, static water level, the yield test and the driller.

Washington has required well reports since 1971; reports are located only to the quarter-quarter section, so check the address on the scan.

The rock under Grant County

Columbia Plateau basin-fill aquifers

Unconsolidated sand and gravel. Wells in sand and gravel are usually shallow and productive, and they recharge quickly from the surface. That makes them the most exposed to nitrate, bacteria and anything spilled nearby, and the least likely to carry arsenic or radon from the rock.

Classification from the USGS Principal Aquifers of the United States (national map, 2003 edition, GIS release 2015), read at the county centroid. A single well can sit in a different unit, especially near a boundary.

Official help in Washington

Two places to start that are not selling anything: the state program that answers private well questions, and its list of labs certified to run drinking water tests. A certified lab is the difference between a result you can act on and a number.

Drinking Water, Washington State Department of Health
Environmental lab accreditation, Washington State Department of Ecology

Contamination sources on record in Grant County

Washington Ecology facility interactions records 7 reported spills and releases in Grant County, among 760 regulated sites in total. Groundwater does not follow property lines, so a well within a few hundred feet of one of these is worth testing for what that site could release.

7: reported spills and releasesMost spills are fuel; a few are solvents or chemicals that reach the water table.
689: other remediation projects
64: other solid waste facilities

Treatment that fits the local profile

Nitrate

Point-of-use reverse osmosis; Anion exchange; Distillation

Arsenic

Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange

PFOS

Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange

Uranium

Point-of-use reverse osmosis; Anion exchange; Whole-house anion exchange

Systems we would look at first

Some links below are affiliate links. If you buy through one, the merchant pays us a commission at no extra cost to you. It does not change which products we list or what the data says.

For nitrate

Under-sink reverse osmosis system

under-sink or countertop, about $300

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

For nitrate

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.

For arsenic

Whole-house arsenic and uranium filter

whole-house, at the point of entry, about $2,500

Adsorptive iron-based media; sized to your well yield.

For PFOS

Aquasana Claryum 3-Stage under-sink filter

under-sink or countertop, about $175

Certified to NSF/ANSI 53 to reduce 99% of lead and 99.7% of PFOA and PFOS at the tap. Not a fix for arsenic, nitrate or bacteria.

For PFOS

Whole-house PFAS carbon system

whole-house, at the point of entry, about $3,000

Granular activated carbon certified to NSF/ANSI 53 for PFOA and PFOS; replace media on schedule.

For PFOS

Aquasana HealthShield whole-house filter

whole-house, at the point of entry, about $2,099

Whole-house carbon system the maker certifies to reduce PFAS (PFOA and PFOS) and VOCs at every tap; a UV option adds bacteria protection.

Free, no obligation

Get on the list for a free in-home water test in Grant County

No water treatment company serves Grant County through Well Water Nerd yet. We are signing licensed companies on county by county: they test at your tap for free, walk you through the numbers, and quote treatment only if something needs fixing. Leave your details and you are first in line. Nothing is shared until a company joins for Grant County, and you get an email naming it first.

Common questions

How deep are wells in Grant County?

The typical domestic well in Grant County is 180 feet deep, based on 5,486 wells reported to the state since 1991. One in ten is deeper than 425 feet.

Is there arsenic in well water in Grant County?

Arsenic was detected in 98% of 143 public well samples in Grant County, and 25% were above the EPA limit of 10 ug/L. Arsenic has no taste or smell; a lab test is the only way to know your level.

How high is radon in well water in Grant County?

The median radon level across 73 public samples in Grant County was 390 pCi/L, with a high of 1,700 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.

How often should I test a private well in Grant County?

Test for bacteria and nitrate every year. Test once for arsenic, uranium, radon, fluoride, manganese and PFAS, then again every three to five years or after any change in taste, color, or plumbing.

Counties near Grant County

Closest first. Groundwater does not stop at a line on a map, so the next county over is a fair second opinion.

Want the numbers themselves? Download the Washington dataset as CSV, every county and town, with the sources named.

Sources

USGS Water Quality Portal: 4,622 samples in Grant County. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
USGS national arsenic model (Ayotte 2017): estimated share of 30,622 people on private wells in Grant County above 10 ug/L of arsenic, from geology, well depth and land use. County estimates of domestic well users with arsenic above 10 ug/L from the USGS national logistic regression model (Ayotte, Medalie and Qi, 2017), with private well population from the USGS 2015 county water-use compilation (Dieter and others, 2018). Retrieved September 15, 2026.
Washington Ecology well construction reports: 5,489 well records in Grant County, 5,486 domestic. Well construction reports filed with the Washington State Department of Ecology, water wells only, located at the quarter-quarter section. Only aggregates are shown; owner names and addresses are never stored. Retrieved September 17, 2026.
Washington Ecology facility interactions: 760 regulated sites located in Grant County. Toxics cleanup sites, spills and solid waste facilities from the Washington State Department of Ecology Facility/Site register. Retrieved September 17, 2026.

Non-detects count as samples and are treated as zero when computing medians. Exactly at the limit counts as not above it. A sample belongs to the town containing the well's reported coordinates.