Groundwater in King County contains sulfate, chloride, iron, lead, and manganese--contaminants that exceed EPA health standards in this area. These levels are concerning enough that well owners need to be aware of them, with chloride, sulfate, and sodium at very high concentrations.
The rock formations underneath King County naturally contain dissolved salts and minerals that leach into groundwater as water moves slowly through the ground over time. The underlying geology here dissolves these minerals readily, releasing them into the water that fills your well.
Groundwater in this county is very hard and salty, driven by elevated sodium, sulfate, and hardness minerals that concentrate from the rock below. These characteristics are widespread across wells in King County, making them common features of water from this area's geology.
Wells in King County commonly have chloride, iron, lead, manganese, and sulfate at levels that exceed EPA health standards. Lead exposure harms children's brain development and can damage kidneys and the nervous system in adults. Chloride and sulfate at elevated levels can affect blood pressure and cause digestive problems. Iron and manganese can harm your nervous system over time. These contaminants pose real health risks to your family.
County well water is extremely hard, which creates stubborn staining on fixtures and dishes. You may notice a bitter or salty taste in your water. Scale builds up inside pipes and appliances, shortening the lifespan of water heaters and dishwashers. Soap doesn't lather well, and laundry stays dingy even after washing.
We recommend a comprehensive metals and minerals panel to find out what is actually in your well, since every well is different and yours could have higher or lower levels than what is common here. Testing is the only way to know what needs treatment. A comprehensive panel typically costs $200 to $400. Depending on your results, water softeners and iron filters can help address 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 ⓘ |
|---|---|---|---|---|---|
| Sulfate | 134 | 99% | High | High | |
| Chloride | 134 | 75% | High | High | |
| Iron | 22 | 14% | Moderate | Moderate | |
| Lead | 12 | 8% | Low | Moderate | |
| Manganese | 13 | 8% | Low | Moderate | |
| Arsenic | 11 | 0% | Low | Low | |
| Fluoride | 140 | 0% | High | Low | |
| Nitrate | 6 | 0% | Low | Low ⓘ | |
| Uranium | 2 | 0% | Low | Low ⓘ | |
| Sodium | 90 | — | Moderate | Low | |
| pH | 90 | — | Moderate | Low | |
| Hardness | 90 | — | Moderate | 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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