Typical values from 71 sampled wells in Imperial County · Full groundwater profile
What Imperial County Wells Usually Need
Hard water: 9.8 gpg. At 9.8 grains per gallon, well water in Imperial County is hard by USGS standards.
Safe to drink? Only after a lab test that includes arsenic.
What usually fixes it:
- A sediment pre-filter first, so sand and scale do not foul the stages after it.
- A 24,000-grain softener for a family of four at 9.8 gpg (includes 5 gpg per ppm of iron).
See how these stages fit together. Your own test result decides the final list.
Not sure what to install? Get a filter recommendation for Imperial County homesIf your water comes from a utility, its annual Consumer Confidence Report is the right source; the figures here are for private wells. Find your utility's report
On this page (8 sections)
Well Water Testing in Imperial County: Who to Call
- Imperial County Public Health Department, Environmental Health Division. Well testing details
- County lab: accepts private well samples; call for the current fee.
- Certified labs: State Water Board list of accredited labs (ELAP)
Contacts as listed on the official page, checked November 2026. Call before you go; hours and fees change.
What Are You Noticing in Your Water?
Pre-selected from Imperial County well data. Untick anything you do not notice in your own water.
Confirm with a lab test before buying equipment.
Explore California Interactive Map
Explore Imperial County and nearby counties
Imperial County has about 179,000 residents, and its largest communities are El Centro, Calexico and Brawley. 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 Imperial Valley.
Across 71 sampled wells, groundwater is hard (9.8 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: Imperial County
Across 71 sampled wells, the median hardness is 9.8 gpg (hard). At 9.8 gpg, Imperial wells run softer than San Diego (15.1 gpg) and about as hard as Riverside (10.6 gpg) next door. The largest California DWR Bulletin 118 groundwater basins in the county are Imperial Valley, Arroyo Seco Valley and East Salton Sea.
Another address? Check hardness by ZIP code.
What shows up in local well samples:
- HardnessMedian 9.8 gpg; 62% of 71 sampled wells above 7 gpg
Calcium and magnesium dissolved from limestone. Leaves scale on fixtures and water heaters and reduces soap lather. Not a health risk.
Water softener sizing - Total dissolved solidsMedian 736 mg/L; 76% of sampled wells above 500 mg/L
A high overall mineral load that affects taste and causes scaling. The EPA aesthetic guideline is 500 mg/L.
Reverse osmosis guide
Arsenic, Nitrate, Chromium-6 and Salinity in Imperial County
| Contaminant | Typical well | Wells above limit | California standard |
|---|---|---|---|
| Arsenic | 3 µg/L | 9% of 34 | 10 µg/L (primary MCL) |
| Nitrate (as nitrogen) | 0.85 mg/L | 0% of 51 | 10 mg/L (primary MCL) |
| Chromium-6 | 0.15 µg/L | Limited data (3 wells) | 10 µg/L (primary MCL since Oct. 1, 2024) |
| Salinity (dissolved solids) | 736 mg/L | 25% of 71 | 500 mg/L recommended, 1,000 mg/L upper (secondary) |
| Hardness | 9.8 gpg | 62% of 71 | No limit; above 7 gpg is hard |
Typical well = median. Standards: State Water Board; samples: Water Quality Portal, since 2000.
How Imperial County Compares to California and the U.S.
See How Imperial County Compares to California & the US
| Share of wells with… | Imperial CountyImperial | CaliforniaCA | United StatesUS |
|---|---|---|---|
| Hard water (above 7 gpg) | 62% | 64% | 60% |
| Iron above 0.3 mg/L | 1% | 9% | 19% |
| Manganese above 0.05 mg/L | 9% | 22% | 21% |
| Dissolved solids above 500 mg/L | 76% | 38% | 15% |
| Acidic water (pH below 6.5) | 0% | 2% | 14% |
| Nitrate above 10 mg/L (EPA limit) | 0% | 9% | 4% |
| Arsenic above 10 µg/L (EPA limit) | 9% | 14% | 7% |
| Chromium-6 above 10 µg/L (California limit) | Limited data | 6% | — |
| Median hardness | 9.8 gpg | 9.9 gpg | — |
| Median pH | 7.8 | 7.6 | 7.3 |
Sources: Water Quality Portal (since 2000); US: USGS Circular 1332. Highlighted: well above the US share.
See what a typical Imperial County well needs
Pre-filled with the Imperial medians. Swap in your own results.
Testing Your Well in Imperial 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 Imperial 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
- Total dissolved solids (salinity), compared with California’s 500 mg/L recommended and 1,000 mg/L upper limits
- 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, work out the bleach dose and shock the well and retest 10 to 14 days later.
Nearby Counties
Imperial County borders these counties with published reports:
Riverside County
10.6 gpg hardness · Hardness, NitrateSan Diego County
15.1 gpg hardness · Hardness, Chloride (salinity)Counties with similar well water
Farther away, these California counties share the same main water issues:
Frequently Asked Questions
Is well water in Imperial County safe to drink?
It depends on your own well. In Imperial County lab records, arsenic exceeded the 10 µg/L limit in 9% of 34 sampled wells. These have no taste or smell, so test for them, and for bacteria, before drinking untreated water.
How hard is well water in Imperial County?
Hard. The median Imperial well tests at 9.8 grains per gallon across 71 sampled wells (California median: 9.9 gpg), and 62% are above the 7 gpg mark where most homes add a softener.
Is iron a problem in Imperial County well water?
The median iron level across 70 sampled wells is 0.01 mg/L, below the EPA aesthetic guideline of 0.3 mg/L, and 1% 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 Imperial County well water?
In 9% of 34 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 Imperial County?
The data cannot say: just 3 Imperial 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 Imperial County well water?
Only 3 wells in Imperial 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 Imperial 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 Imperial 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 Imperial 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.