Private well water and your health

Private well water

Private and individual household wells serve fewer than 25 people and are not regulated by the federal Safe Drinking Water Act. Typically, a private well supplies drinking water to one home, and the homeowner maintains it. According to the USGS, about 7% of Colorado residents get their drinking water from a private well.

Well water quality and human health

Whether a contaminant in drinking water will harm your health depends on many factors such as:

  • How much of the contaminant you came into contact with.
  • How long you were exposed to the contaminant. Many contaminants don’t have immediate health impacts, but short exposures to bacteria or nitrate can make a person sick quickly.   
  • Your age, genetics, and health history.

The potential health impacts of drinking contaminated water are specific to the contaminant. Non-cancer impacts include stomach illness or impacts to the heart, skin, lungs, kidneys, or nervous system. Other contaminants may affect children’s development. Drinking water that has high levels of certain metals for many years may increase the risk of cancer. Learn more about the potential health impacts from specific contaminants on our private well water interactive tool.


More information below

You can take precautions to reduce your exposure to potential contaminants in your private well drinking water.

  • Routinely inspect exposed parts of wells for problems such as:
    • Cracked, corroded, or damaged well casings.
    • Broken or missing well caps.
    • Settling and cracking of surface seals.
  • Create slopes around wells to drain surface runoff away from the well.
  • Install a well cap or sanitary seal to prevent unauthorized use of, or entry into, your well.
  • Keep records of all well maintenance, including disinfection, removal of sediment, and processes that use chemicals.
  • Hire a certified contractor for new well construction, installation of pumping equipment, modifications, abandonments, or closing your well.
  • Avoid mixing or using pesticides, fertilizers, herbicides, degreasers, fuels, and other pollutants near a well.
  • Do not dump wastes, harsh chemicals, petroleum products, or pesticides in a septic system or in dry or abandoned wells.
  • Keep well casings at least 12 inches above the ground’s surface.
  • Pump and inspect septic systems as often as recommended by your local public health agency.
  • Disinfect your well and/or consider a home treatment system.

Private well water may contain contaminants that are naturally occurring or human-made. The owner is responsible for testing well water and making any changes to improve its quality. Public water systems do not test private well water.

Private well water quality varies from well to well depending upon:

  • The depth of the well.
  • Groundwater  and geologic features. 
  • How the land near the well is used.
  • The condition of the well.  

Testing Frequency 

Test your well water at least once a year. More frequent testing may be needed if:

  • Pregnant or breastfeeding people drink the water.
  • People who drink the water have unexplained stomach illnesses.
  • Contaminants are found in a neighboring well.
  • There are changes in water taste, odor, color, or clarity.
  • Chemicals or fuels have been spilled into or near the well.
  • A recent natural disaster, such as a flood or fire, has occurred.

More information about when to test your well water.

You have three common options to reduce or remove contaminants in water. 

  1. Have a certified contractor disinfect your well to eliminate bacteria.

Note: Chlorine bleach disinfection does not remove arsenic.

  1. Install a single point-of-use treatment system.
    1. When placed under a kitchen sink, the system filters out contaminants for drinking and cooking.
    2. When placed at a point where the well water enters the home plumbing, the system filters out contaminants for household uses.
  2. Install multiple treatments for the household water system. Install near the water storage tank, to filter out multiple contaminants or to improve water quality for all household uses.

Maintain your treatment system

Properly maintain your treatment system to ensure good water quality.

  • Ask about maintenance needs before the water treatment system is installed.
  • Replace filter cartridges, membranes, or ultraviolet lights as instructed by the manufacturer - usually once a year.
  • Keep accurate maintenance records.
  • Test both the treatment system and the water regularly.

More information about Home Water Treatment.

The Colorado Environmental Public Health Tracking Program at CDPHE compiles all publicly available well water quality data into a data repository. They provide summary statistics based on these reported test results. How often well water is tested and reported is inconsistent because private well water testing is not required. Public labs that regularly test well water samples provide data to CDPHE annually or semi-annually. Private laboratories typically do not share the data they collect with the Colorado Environmental Public Health Tracking Program.


In addition to these resources, you may want to  contact your local public health agency for more information. Some agencies may recommend where to place a new well and how to construct it, or have other helpful information.  



For questions about water and your health: contact ToxCall at 303-692-2606 or cdphe_toxcall@state.co.us or speak to your medical provider.