Well Water in Yolo County: What to Test and Why

Groundwater in Yolo County contains boron, manganese, chloride, arsenic, fluoride, iron, nitrate, and sulfate at levels that exceed EPA health standards. These contaminant levels are serious enough that well owners should test their water and consider treatment options.

These contaminants come from the rock and soil layers beneath the county. Boron, manganese, and arsenic occur naturally in the local rock. Nitrate and chloride enter groundwater from agricultural activity and urban sources like septic systems and road salt. Fluoride also occurs naturally in some rock layers.

Groundwater in this county is very hard, driven by calcium and magnesium dissolved from the rock below, and it also carries moderate sodium. The combination of these minerals reflects the county's mixed geology and the slow movement of water through rock layers that release these elements into groundwater. Very hard water with elevated sodium and total dissolved solids is common across Yolo County wells.

Wells in Yolo County commonly have arsenic, boron, chloride, fluoride, iron, manganese, nitrate, and sulfate at levels that exceed EPA health standards. Arsenic exposure raises the risk of cancer and can harm the nervous system and heart. Boron affects reproduction and child development. High nitrate is especially dangerous for infants and can interfere with oxygen in the blood. Fluoride at elevated levels can damage teeth and bones. Manganese harms the brain and nervous system, particularly in children.

The very hard water in county wells causes scale buildup in pipes and on fixtures, leaving white crusty deposits. This extreme hardness also shortens the lifespan of water heaters, dishwashers, and other appliances. You may notice reduced water pressure and soap that does not lather well. Some well owners report a mineral taste or slight odor in their water.

We recommend getting your well tested right away. Every well in the county is different, and your well could have higher or lower levels than what is common here. A comprehensive testing panel is recommended given the number of contaminants in this county--this typically costs $200 to $400 and is the only way to know exactly what is in your water so you can treat it properly. Treatment options like reverse osmosis, activated carbon filters, and water softeners can address multiple concerns depending on what testing shows.