Typical values from 20 sampled wells in Lassen County · Full groundwater profile
Quick Answers for Lassen County Well Owners
No common nuisance problem in the typical well. The typical Lassen well is moderately hard, with iron below the stain threshold and a pH of 7.7.
Safe to drink? Only after a lab test that includes arsenic.
What usually fixes it:
Usually nothing beyond routine testing. Most Lassen wells need no softener or iron filter, so test before buying equipment.
Not sure what to install? Get a filter recommendation for Lassen County homesOn 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 Lassen County
- Your county environmental health department handles private well questions in Lassen 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 Lassen County and nearby counties
Lassen County has about 29,000 residents, and its largest communities are Susanville. Homes outside city and community water systems rely on private domestic wells. Wells here tap the Pacific Northwest basaltic-rock aquifers, and the largest DWR groundwater basin in the county is Honey Lake Valley.
Across 20 sampled wells, groundwater is moderately hard (5.2 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: Lassen County
Across 20 sampled wells, the median hardness is 5.2 gpg (moderately hard). At 5.2 gpg, Lassen wells run harder than Shasta (4.3 gpg) next door. The largest California DWR Bulletin 118 groundwater basins in the county are Honey Lake Valley, Madeline Plains and Big Valley.
Another address? Check hardness by ZIP code.
No contaminant tracked here was above its EPA guideline in the typical (median) sampled well.
Arsenic, Nitrate, Chromium-6 and Salinity in Lassen County
| Contaminant | Typical well | Wells above limit | California standard |
|---|---|---|---|
| Arsenic | 2.7 µg/L | 10% of 21 | 10 µg/L (primary MCL) |
| Nitrate (as nitrogen) | 0.42 mg/L | 5% of 20 | 10 mg/L (primary MCL) |
| Chromium-6 | 0.75 µg/L | Limited data (4 wells) | 10 µg/L (primary MCL since Oct. 1, 2024) |
| Salinity (dissolved solids) | 323 mg/L | 0% of 21 | 500 mg/L recommended, 1,000 mg/L upper (secondary) |
| Hardness | 5.2 gpg | 20% of 20 | No limit; above 7 gpg is hard |
Typical well = median. Standards: State Water Board; samples: Water Quality Portal, since 2000.
How Lassen County Compares to California and the U.S.
See How Lassen County Compares to California & the US
| Share of wells with… | Lassen CountyLassen | CaliforniaCA | United StatesUS |
|---|---|---|---|
| Hard water (above 7 gpg) | 20% | 64% | 60% |
| Iron above 0.3 mg/L | 10% | 9% | 19% |
| Manganese above 0.05 mg/L | Limited data | 22% | 21% |
| Dissolved solids above 500 mg/L | 29% | 38% | 15% |
| Acidic water (pH below 6.5) | 0% | 2% | 14% |
| Nitrate above 10 mg/L (EPA limit) | 5% | 9% | 4% |
| Arsenic above 10 µg/L (EPA limit) | 10% | 14% | 7% |
| Chromium-6 above 10 µg/L (California limit) | Limited data | 6% | — |
| Median hardness | 5.2 gpg | 9.9 gpg | — |
| Median pH | 7.7 | 7.6 | 7.3 |
Sources: Water Quality Portal (since 2000); US: USGS Circular 1332. Highlighted: well above the US share.
See what a typical Lassen County well needs
Pre-filled with the Lassen medians. Swap in your own results.
Testing Your Well in Lassen 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 Lassen County:
- Bacteria (total coliform and E. coli), nitrate and arsenic, at least once a year (California State Water Resources Control Board recommendation)
- 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
Lassen County borders these counties with published reports:
Counties with similar well water
Not next door, but the groundwater is much the same:
Frequently Asked Questions
Is well water in Lassen County safe to drink?
Not without a test. Arsenic exceeded the 10 µg/L limit in 10% of 21 sampled wells and nitrate exceeded the 10 mg/L limit in 5% of 20 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 Lassen County?
Groundwater samples from 20 wells in Lassen County have a median hardness of 5.2 grains per gallon (89 mg/L), which the USGS classes as moderately hard. About 20% 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 Lassen County well water?
The median iron level across 20 sampled wells is 0 mg/L, below the EPA aesthetic guideline of 0.3 mg/L, and 10% 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 Lassen County well water?
Arsenic topped 10 µg/L in 10% of the 21 wells sampled here. You cannot see or taste it, so test for it, and use reverse osmosis or an arsenic filter if your result is high.
Is nitrate a problem in Lassen County well water?
Nitrate was over the 10 mg/L limit in 5% of 20 wells sampled here, usually from fertilizer or septic systems nearby. Reverse osmosis or anion exchange removes it; boiling makes it worse.
Why does my well water smell like rotten eggs in Lassen County?
The data cannot say: just 2 Lassen wells were tested for hydrogen sulfide. If your water smells, test for sulfide, and if the smell is only in hot water, check the water heater anode rod. It is unpleasant but rarely a health risk.
Is chromium-6 a concern in Lassen County well water?
Only 4 wells in Lassen 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.
Does boiling well water make it safe to drink in Lassen 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 Lassen 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.