Typical values from 16 sampled wells in Lake County · Full groundwater profile
Lake County Well Water at a Glance
No common nuisance problem in the typical well. The typical Lake well is hard, with iron below the stain threshold and a pH of 7.1.
Drink it untreated? Generally yes in the records, though only your own test covers your well.
What a typical home here installs:
Usually nothing beyond routine testing. Most Lake wells need no softener or iron filter, so test before buying equipment.
Not sure what to install? Get a filter recommendation for Lake County homesNot on a well? Tap water from a utility is covered by its yearly water quality report (CCR), not by these well samples. Find your utility's report
On this page (8 sections)
Where to Test Well Water in Lake County
- Your county environmental health department handles private well questions in Lake 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 Lake County and nearby counties
Lake County has about 68,000 residents, and its largest communities are Clearlake and Lakeport. Homes outside city and community water systems rely on private domestic wells. Wells here tap the California Coastal Basin aquifers, and the largest DWR groundwater basin in the county is Clear Lake Cache Formation.
Across 16 sampled wells, groundwater is hard (9.1 gpg in the typical well). Arsenic, nitrate and chromium-6 were below California limits in most sampled wells, but individual wells vary, so test yours.
In this guide
Groundwater Profile: Lake County
The largest California DWR Bulletin 118 groundwater basins in the county are Clear Lake Cache Formation, Big Valley and Upper Lake Valley.
Another address? Check hardness by ZIP code.
What shows up in local well samples:
- HardnessLimited local data (fewer than 20 samples): individual well testing recommended.
Calcium and magnesium dissolved from limestone. Leaves scale on fixtures and water heaters and reduces soap lather. Not a health risk.
Water softener sizing
Arsenic, Nitrate, Chromium-6 and Salinity in Lake County
| Contaminant | Typical well | Wells above limit | California standard |
|---|---|---|---|
| Arsenic | 0.1 µg/L | Limited data (13 wells) | 10 µg/L (primary MCL) |
| Nitrate (as nitrogen) | 0.08 mg/L | Limited data (7 wells) | 10 mg/L (primary MCL) |
| Chromium-6 | 0.15 µg/L | Limited data (2 wells) | 10 µg/L (primary MCL since Oct. 1, 2024) |
| Salinity (dissolved solids) | 240 mg/L | Limited data (15 wells) | 500 mg/L recommended, 1,000 mg/L upper (secondary) |
| Hardness | 9.1 gpg | Limited data (16 wells) | No limit; above 7 gpg is hard |
Typical well = median. Standards: State Water Board; samples: Water Quality Portal, since 2000.
How Lake County Compares to California and the U.S.
See How Lake County Compares to California & the US
| Share of wells with… | Lake CountyLake | CaliforniaCA | United StatesUS |
|---|---|---|---|
| Hard water (above 7 gpg) | Limited data | 64% | 60% |
| Iron above 0.3 mg/L | Limited data | 9% | 19% |
| Manganese above 0.05 mg/L | Limited data | 22% | 21% |
| Dissolved solids above 500 mg/L | 13% | 38% | 15% |
| Acidic water (pH below 6.5) | 9% | 2% | 14% |
| Nitrate above 10 mg/L (EPA limit) | Limited data | 9% | 4% |
| Arsenic above 10 µg/L (EPA limit) | Limited data | 14% | 7% |
| Chromium-6 above 10 µg/L (California limit) | Limited data | 6% | — |
| Median hardness | 9.1 gpg | 9.9 gpg | — |
| Median pH | 7.1 | 7.6 | 7.3 |
Sources: Water Quality Portal (since 2000); US: USGS Circular 1332. Highlighted: well above the US share.
See what a typical Lake County well needs
Pre-filled with the Lake medians. Swap in your own results.
Testing Your Well in Lake 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 Lake County:
- Bacteria (total coliform and E. coli), nitrate and arsenic, at least once a year (California State Water Resources Control Board recommendation)
- Hardness in grains per gallon (gpg) to size a softener
- 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
Lake County borders these counties with published reports:
Colusa County
17.4 gpg hardness · Hardness, ManganeseGlenn County
14.6 gpg hardness · HardnessMendocino County
6.5 gpg hardnessNapa County
5.2 gpg hardness · Manganese, ArsenicSonoma County
7.3 gpg hardness · HardnessYolo County
14.6 gpg hardness · HardnessCounties with similar well water
Not next door, but the groundwater is much the same:
Frequently Asked Questions
Is well water in Lake County safe to drink?
Generally yes in the records: health limits are rarely exceeded in the 16 Lake wells sampled. Bacteria and nitrate can still turn up in any well, so test once a year.
How hard is well water in Lake County?
Groundwater samples from 16 wells in Lake County have a median hardness of 9.1 grains per gallon (156 mg/L), which the USGS classes as hard. Limited local data (fewer than 20 samples): individual well testing recommended. The California statewide median is 9.9 gpg.
Is iron a problem in Lake County well water?
The median iron level across 15 sampled wells is 0 mg/L, below the EPA aesthetic guideline of 0.3 mg/L (limited local data (fewer than 20 samples): individual well testing recommended). Most wells will not stain, but if yours does, a lab test tells you whether iron or manganese is the cause.
Why does my well water smell like rotten eggs in Lake County?
Public lab records include sulfide results for only 1 wells in Lake, 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 Lake County well water?
Only 2 wells in Lake County have been sampled for hexavalent chromium, too few to say how common it is. California’s limit is 10 µg/L, and only a lab test of your own well can show whether it is affected.
Can I install a salt-based water softener in Lake County?
Usually, but check local rules first. California Water Code Section 13148 lets some local sewer and water recycling agencies limit or ban new salt-discharging softeners to protect recycled water. Homes on septic systems should ask the county environmental health department about brine. A salt-free conditioner discharges no brine, but it reduces scale rather than softening the water.
Does boiling well water make it safe to drink in Lake County?
For a bacteria problem, yes: boil for one minute (three above 6,500 feet). For anything chemical, no, because evaporation concentrates it. Our boiling well water myth buster explains the difference.
How often should I test my well water in Lake 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.