Typical values from 26 sampled wells in Inyo County · Full groundwater profile
What Inyo County Wells Usually Need
Arsenic above the drinking water limit. Arsenic exceeded the 10 µg/L limit in 13% of 23 sampled Inyo wells. It has no taste or smell, so only a lab test shows whether your well is affected.
Drink it untreated? Not untreated until a lab has checked it for arsenic.
What a typical home here installs:
- Point-of-use reverse osmosis for drinking water, but only after a lab test confirms the problem in your well.
On city or county water instead? Your utility publishes an annual water quality report; this page covers private wells. Find your utility's report
On this page (8 sections)
Where to Test Well Water in Inyo County
- Your county environmental health department handles private well questions in Inyo County; for a water test, use a state-accredited lab, many of which accept mailed or dropped-off samples.
- Certified labs: State Water Board list of accredited labs (ELAP)
Ask the lab for sample bottles and how quickly the sample must reach it before you collect.
What Are You Noticing in Your Water?
Confirm with a lab test before buying equipment.
Explore California Interactive Map
Explore Inyo County and nearby counties
Inyo County has about 19,000 residents, and its largest communities are Bishop. Homes outside city and community water systems rely on private domestic wells. Wells here tap the Basin and Range basin-fill aquifers, and the largest DWR groundwater basin in the county is Death Valley.
Across 26 sampled wells, groundwater is moderately hard (4.5 gpg in the typical well). Arsenic exceeded the 10 µg/L drinking water limit in 13% of 23 sampled wells. These have no taste or smell, so only a lab test shows whether your own well is affected.
In this guide
Groundwater Profile: Inyo County
Across 26 sampled wells, the median hardness is 4.5 gpg (moderately hard). At 4.5 gpg, Inyo wells run softer than Mono (5.8 gpg), San Bernardino (7.3 gpg) and Tulare (9.3 gpg) next door. The largest California DWR Bulletin 118 groundwater basins in the county are Death Valley, Owens Valley – Owens Valley and Middle Amargosa Valley.
Another address? Check hardness by ZIP code.
What shows up in local well samples:
- Arsenic13% of 23 sampled wells above 10 µg/L
Odorless and tasteless, with an EPA limit of 10 µg/L. Only a lab test detects it.
How to test your well
Arsenic, Nitrate, Chromium-6 and Salinity in Inyo County
| Contaminant | Typical well | Wells above limit | California standard |
|---|---|---|---|
| Arsenic | 1.4 µg/L | 13% of 23 | 10 µg/L (primary MCL) |
| Nitrate (as nitrogen) | 0.34 mg/L | Limited data (18 wells) | 10 mg/L (primary MCL) |
| Chromium-6 | 0 µg/L | 0% of 48 | 10 µg/L (primary MCL since Oct. 1, 2024) |
| Salinity (dissolved solids) | 160 mg/L | 12% of 25 | 500 mg/L recommended, 1,000 mg/L upper (secondary) |
| Hardness | 4.5 gpg | 19% of 26 | No limit; above 7 gpg is hard |
Typical well = median. Standards: State Water Board; samples: Water Quality Portal, since 2000.
How Inyo County Compares to California and the U.S.
See How Inyo County Compares to California & the US
| Share of wells with… | Inyo CountyInyo | CaliforniaCA | United StatesUS |
|---|---|---|---|
| Hard water (above 7 gpg) | 19% | 64% | 60% |
| Iron above 0.3 mg/L | 4% | 9% | 19% |
| Manganese above 0.05 mg/L | 9% | 22% | 21% |
| Dissolved solids above 500 mg/L | 28% | 38% | 15% |
| Acidic water (pH below 6.5) | 0% | 2% | 14% |
| Nitrate above 10 mg/L (EPA limit) | Limited data | 9% | 4% |
| Arsenic above 10 µg/L (EPA limit) | 13% | 14% | 7% |
| Chromium-6 above 10 µg/L (California limit) | 0% | 6% | — |
| Median hardness | 4.5 gpg | 9.9 gpg | — |
| Median pH | 7.5 | 7.6 | 7.3 |
Sources: Water Quality Portal (since 2000); US: USGS Circular 1332. Highlighted: well above the US share.
See what a typical Inyo County well needs
Pre-filled with the Inyo medians. Swap in your own results.
Testing Your Well in Inyo County
In California, county environmental health departments handle private well permits and can advise on testing. For bacteria, nitrate, arsenic or a full panel, use a laboratory accredited by California’s Environmental Laboratory Accreditation Program (ELAP); the State Water Board’s certified lab map lists them.
What to test for in Inyo County:
- Bacteria (total coliform and E. coli), nitrate and arsenic, at least once a year (California State Water Resources Control Board recommendation)
- Arsenic, which appeared above the 10 µg/L limit in some sampled wells here
- After any flood, new well work or a change in taste, color or smell
Which tests to order and how: how to test well water.
After a positive coliform test, shock the well with the right bleach dose and retest 10 to 14 days later.
Nearby Counties
Inyo County borders these counties with published reports:
Fresno County
10.5 gpg hardness · Hardness, NitrateKern County
12.1 gpg hardness · Hardness, ArsenicMono County
5.8 gpg hardness · ArsenicSan Bernardino County
7.3 gpg hardness · Hardness, ArsenicTulare County
9.3 gpg hardness · Hardness, Hydrogen sulfideCounties with similar well water
Not next door, but the groundwater is much the same:
Frequently Asked Questions
Is well water in Inyo County safe to drink?
Not without a test. Arsenic exceeded the 10 µg/L limit in 13% of 23 sampled wells. Only a lab result shows whether your well is one of them; treat or switch to bottled water until you know.
How hard is well water in Inyo County?
Groundwater samples from 26 wells in Inyo County have a median hardness of 4.5 grains per gallon (76 mg/L), which the USGS classes as moderately hard. About 19% of sampled wells are above 7 gpg, the point where a water softener is usually worthwhile. The California statewide median is 9.9 gpg.
Is iron a problem in Inyo County well water?
The median iron level across 26 sampled wells is 0 mg/L, below the EPA aesthetic guideline of 0.3 mg/L, and 4% of wells exceed it. Most wells will not stain, but if yours does, a lab test tells you whether iron or manganese is the cause.
Is arsenic a problem in Inyo County well water?
In 13% of 23 sampled wells, arsenic was above the 10 µg/L drinking water limit. It has no taste, color or smell, so only a lab test finds it; reverse osmosis at the kitchen tap or a whole-house arsenic filter removes it.
Why does my well water smell like rotten eggs in Inyo County?
Public lab records include sulfide results for only 6 wells in Inyo, not enough to judge. The smell comes from hydrogen sulfide; a sulfide test confirms it, and at household levels it is a nuisance, not a health hazard.
Is chromium-6 a concern in Inyo County well water?
Hexavalent chromium was above California’s 10 µg/L drinking water limit in 0% of 48 sampled wells in Inyo County. The limit took effect on October 1, 2024. It has no taste or smell, so only a lab test shows whether your well is affected; reverse osmosis is a common household treatment.
Does boiling well water make it safe to drink in Inyo County?
No, not for the arsenic found in some Inyo wells. Boiling kills bacteria, but chemicals stay behind and become more concentrated as water evaporates. Here is why boiling cannot remove nitrate or arsenic.
How often should I test my well water in Inyo County?
The California State Water Resources Control Board recommends testing domestic wells every year, including for bacteria, nitrate and arsenic, and again after flooding or well repairs.
Written by Well Water Advisor Editorial Team.