Safe & Clean Drinking Water Practices for Private Well Owners


By Leslie Lindbo, Yolo County Director of Environmental Health
January 2013

If you live in one of Yolo County’s incorporated cities, your tap water and the systems that deliver it, are likely provided by a public agency, and therefore regularly and rigorously examined per state law. Private wells, however, are a different story. The quality and protection of private well drinking water is the responsibility of the well owner yet inspections are not mandated. Just as with public wells, private wells must receive adequate testing and inspection to ensure safe and clean water.

Private well owners should have their drinking water tested at least annually for contaminants such as bacteria, nitrates, arsenic and lead, or any other suspected contaminant. To find a state-certified drinking water laboratory, visit:  In some special circumstances, private well owners might want to conduct more frequent tests, such as if: someone in the household is pregnant or nursing; there are unexplained illnesses in the family; neighbors find a dangerous contaminant in their water; a change is detected in water taste, odor, color or clarity; there is a chemical or fuel spill into or near the well; and any part of the well system is replaced or repaired.

Common contaminants in drinking:

The most common drinking water well chemical contaminants found in Yolo County include nitrate, as a result of runoff and leaching from agriculture production, and arsenic, as a result of erosion of natural deposits, runoff from orchards, and glass and electronic production waste. Nitrate is of concern because with acute exposure, infants less than six months of age may become seriously ill, and left untreated, may die as high nitrate levels interfere with the capacity of blood to carry oxygen. Arsenic is of concern because chronic exposure over many years may result in skin damage, circulatory system problems or an increased risk of cancer for all ages.

For information on water treatment methods, consult:  or html   

Private well owners can protect their water supply by:

  • Hiring a certified well driller for well construction, modification, abandonment or closure. Note: a permit must be obtained from Yolo County Environmental Health for any of these activities.
  • Periodically inspecting exposed parts of the well for problems such as a cracked, corroded or damaged well casing, a broken or missing well cap, or settling or cracking of surface seals.
  • Sloping the area around the well to drain surface runoff away from the well.
  • Installing a well cap and an adequate sanitary seal to prevent unauthorized use of, or entry into the well.
  • Keeping accurate records of maintenance that may require the use of chemicals in the well, such as disinfection or sediment removal.
  • Avoiding mix or use of pesticides, fertilizers, herbicides, degreasers, fuel or other pollutants near the well.
  • Not disposing of waste in a dry or abandoned well.
  • Not cutting off the well casing below the land surface.
  • Pumping and inspecting septic systems as often as recommended by Yolo County Environmental Health.
  • Not disposing of harsh chemicals, solvents, petroleum products or pesticides in a septic system or dry well.

For more information on services provided by Yolo County Environmental Health, visit: (go to Environmental Health Services).