Groundwater in Los Angeles County contains manganese, radon, arsenic, and many other contaminants including lead, uranium, nitrate, and fluorinated chemicals. Many of these exceed EPA health standards, making this a county where well owners need to test their water and understand what is coming from their tap.
Los Angeles County sits on mixed rock layers that hold and move water in complex ways. Contaminants come from multiple sources: some metals like arsenic and uranium occur naturally in the rock itself, while others like nitrate and fluorinated chemicals enter from urban runoff, industrial activity, and past disposal practices. Radon seeps from the rock into groundwater. The region's dense development and long history of chemical use have added to the natural contamination picture.
Groundwater in this county is hard, driven by elevated calcium and magnesium dissolved from the rock. Moderate levels of sodium and sulfate also concentrate in the water because of the geology and the slow movement of water through these mixed rock layers. These mineral characteristics show up across many wells in the county.
Wells in Los Angeles County show several contaminants at levels that exceed EPA health standards. Arsenic, uranium, and radon are radioactive elements that increase cancer risk with long-term exposure. Lead harms children's brain development and causes high blood pressure in adults. Nitrate and nitrite affect oxygen in the blood, especially in infants. Fluoride, chloride, and sulfate are present at elevated levels. PFAS chemicals, including PFOA, PFOS, PFNA, and PFHXS, are industrial compounds that may harm the immune system and liver with continued exposure.
County wells show moderate hardness and mineral content that affects daily life. The hard water can leave white scale on faucets and fixtures, stain laundry, and reduce how well soap works. It shortens the lifespan of water heaters and dishwashers. You may notice a slightly salty or mineral taste in the water.
We recommend testing your well with a comprehensive metals and minerals panel, which costs between $200 and $400. Every well is different, and your water could have higher or lower levels than what is common in the county. Testing is the only way to know what is actually in your well so you can treat it correctly. Water softeners and activated carbon filters can address many of these concerns.
Not sure if your well is affected? Get certified results in 5–7 days.
Test Your Well Water with Tap Score →| Contaminant | Samples ⓘ | % Above MCL ⓘ | Distribution ⓘ | Confidence ⓘ | Risk ⓘ |
|---|---|---|---|---|---|
| Manganese | 1980 | 29% | High | High | |
| Radon | 138 | 25% | High | High ⓘ | |
| Arsenic | 1111 | 20% | High | High | |
| PFOS ⓘ municipal | 1047 | 17% | High | High | |
| PFOA ⓘ municipal | 1047 | 14% | High | Moderate | |
| Sulfate | 2714 | 5% | High | Moderate | |
| Chloride | 2841 | 4% | High |
Moderate
Elevated concentration, not % above limit
|
|
| Lead | 568 | 4% | High |
Moderate
Elevated concentration, not % above limit
|
|
| Nitrite | 1447 | 4% | High |
Moderate
Elevated concentration, not % above limit
|
|
| Iron | 2165 | 4% | High |
Moderate
Elevated concentration, not % above limit
|
|
| Nitrate | 2565 | 3% | High | Low | |
| Uranium | 331 | 1% | High | Low | |
| PFHxS ⓘ municipal | 1042 | 1% | High | Low | |
| PFNA ⓘ municipal | 1047 | 0% | High | Low | |
| Fluoride | 2537 | 0% | High | Low | |
| Boron | 5 | 0% | Low | Low ⓘ | |
| Chromium (total) | 5 | 0% | Low | Low ⓘ | |
| 1,2,3-Trichloropropane | 8 | 0% | Low | Safe ⓘ | |
| HFPO-DA (GenX) ⓘ municipal | 1047 | 0% | High | Safe | |
| Perchlorate | 8 | 0% | Low | Low ⓘ | |
| Hardness | 2911 | — | High | Low | |
| Tds | 5 | — | Low | Low ⓘ | |
| Sodium | 2842 | — | High | Low | |
| pH | 3228 | — | High | Low | |
| PFBS ⓘ municipal | 1047 | — | High | Low | |
| Total Coliform | 2* | 0% | Low | Low ⓘ | |
| E. coli | 2* | 0% | Low | Low ⓘ |
MCL = Maximum Contaminant Level (EPA limit for public water; used as benchmark for private wells). Distribution shows % of sampled wells in each concentration band. Methodology.
* Microbial contaminants (E. coli, coliform) reflect only samples from the last 10 years.
Data shows potential risk — a certified test confirms whether your water is affected.
Order a Tap Score Test →Population-level CDC data. Not individual risk prediction.
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