Groundwater in King County contains sulfate, chloride, iron, lead, and manganese at levels that exceed EPA health standards. These contaminants are present at concerning concentrations that well owners should address.
The rocks beneath King County naturally contain minerals that dissolve into groundwater as water moves through them. Sulfate and chloride build up in the water because the bedrock here is rich in these salts. Iron and manganese come from the rock minerals themselves, which break down and release these metals into the water supply.
Groundwater in this county is very hard, with extremely elevated sodium and sulfate that define its character. The local rock layers contain salt deposits and mineral-rich stone that leach these compounds into water as it flows underground. These characteristics are widespread across King County wells.
Wells in King County are showing levels of chloride, iron, lead, manganese, and sulfate that exceed EPA health standards. Lead exposure harms children's brain development and learning ability. Manganese at high levels can affect the nervous system and cause movement problems. Chloride and sulfate at elevated levels can cause digestive issues, and iron can harbor bacteria that create health risks.
The extremely hard water in this county's wells creates serious problems for your home and appliances. Hard water leaves white crusty buildup on faucets, fixtures, and inside pipes. It makes soap less effective and leaves spots on dishes and skin. The very high sodium and sulfate levels often create a salty or rotten-egg taste and odor. Hard water shortens the lifespan of water heaters, dishwashers, and washing machines by years.
We recommend getting your well tested right away since every well is different and yours could have higher or lower levels than the county average. A comprehensive metals and minerals panel costs between $200 and $400 and is the only way to know exactly what is in your water so you can treat it properly. Water softening systems and filters designed for specific contaminants can address these problems.
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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