GAMA Program Banner

GAMA - Domestic Well Testing

The quality of drinking water is vital to your health and wellbeing. If you use a domestic well for drinking water, it is recommended that you test your well water quality annually. If your results come back with high concentrations of constituents, or you are aware of a contaminant in your water, you will want to compare the test concentration to known Maximum Contaminant Levels (MCL), set by the United States (US) and/or the California Environmental Protection Agency (EPA). An MCL is the highest level of contaminant allowed in drinking water, typically based on health risk from exposure. While MCLs are an enforceable standard for public supply systems, it is recommended you observe the same levels in your domestic well.
The following checklist contains steps that can help domestic well owners evaluate the quality of their well water:

  • Step 1: Test the well water quality by either using a laboratory or a self-test kit. The difference between these methods is that a lab will be able to provide concentrations of contaminants while a self-test kit will only let you know if a constituent is present.
    • Self-testing water quality kits are available from hardware and home warehouse stores and can be useful in evaluating whether a contaminant is present.
    • If you are aware of a possible contaminant in your water, you may get your well water tested at a laboratory that does water sampling. There are many labs in California or the nation to choose from, depending on your needs.
      • You may choose to work with an Environmental Laboratory Accreditation Program (ELAP) certified laboratory to ensure the best results; however, this may get costly. A lab will supply the sampling bottles and can assist in sampling your well to provide accurate and reliable results.
        • Search the Division of Drinking Water’s Geographic Information System (GIS) Map to find Environmental Laboratory Accreditation Program (ELAP) accredited laboratories in your area:
        •   California ELAP Certified Laboratories GIS Map
    • Pricing varies depending on the number of constituents analyzed and lab or outside business employed. Basic sampling can cost from $100 to $400. Ask for a written estimate before sampling.
    • Water quality testing may include testing for various constituents such as:
      • Bacteria (such as E.coli, total coliforms, giardia)
      • Inorganics (such as arsenic, uranium, total dissolved solids),
      • Agricultural products:
        • fertilizers (such as nitrate, phosphate),
        • pesticides (such as atrazine, simazine, metolachlor, dacthal),
      • Industrial products:
        • solvents (such as ethanol, toluene, acetone, benzene).
  • Step 2: Evaluate the quality of your well water. A simple method to evaluate the quality of your water is to compare your results to known MCLs and identify those constituents that either exceed the MCL or are close to it. MCLs may be found at this link to the US EPA National Primary Drinking Water Regulations.
    • To assist well owners in understanding their test results, a link to reference information about standards that apply to public drinking water supplies is included below.
    • It is important to understand that the quality of the water in your well is not required to meet these standards, but it is recommended for your health.
    • If your results are above the recommended water standards, proceed to Step 3.
  • Step 3: You may choose to verify the accuracy of your test results by re-testing your well for those specific high concentration constituents. If a result is above a primary MCL, it is recommended that you do not consume the water until appropriate actions are taken. Water use for other daily task such as showering may be limited depending on the type on contaminant. Contact your local Environmental Health Department for advice about how to make your water safe to drink. Such actions may include:
    • Filtering water. There are many methods to filter water depending on what constituent you want to remove.
      • Mechanical filtering removes particle sizes based on the filters rating;
      • Absorption filtering, of which carbon filtering is a type, traps water borne constituents as the water moves through it;
      • Ion Exchange is used to soften hard water by exchanging the ‘hard’ minerals (typically magnesium and calcium) for ‘softer’ minerals (typically sodium or hydrogen);
      • Reverse Osmosis removes dissolved inorganic solids (such as salts) by forcing water through a semipermeable membrane under pressure such that water is allowed through by the inorganic solids are not.
    • Removing point source contamination
      • If you have a known contaminant on your land, such as a leaking gas tank, old or leaking chemical storage (such as pesticides, fertilizers, paint, etc), or old damaged septic tank, removal may lessen the problem.
    • Repair damaged well casing
      • Damaged well casing may allow contaminated surface water into the well.
  • Step 4: Prevent degraded water quality.
    • Conduct routine well maintenance to ensure there is no damage and immediately repair any damage that is found. Maintenance includes:
      • Check annually for mechanical problems, cleanliness, and water quality.
      • Water quality should be tested more frequently if people are experiencing a noticeable change in the water odor or appearance.
      • Hazardous materials should be kept well away from the well, including motor oil, gasoline, pesticides, paint, and fertilizer.
      • Prevent siphoning of foreign material by not placing a hose directly into another substance.
      • Consult a professional contractor to verify the setback distances from your well, home, waste systems, and other facilities are appropriate.
      • Check the well head remains at a minimum one-foot above ground, and the well cap or cover is intact and placed appropriately. Ensure that water drains away from the casing, commonly by building a slightly sloped cement pad.
      • If your well is 20 years old or more, have a licensed or certified water well driller and pump installer check the well. Most wells are constructed to have a lifetime of about 20 years, and it is possible your well may need to be decommissioned and a new well drilled.
    • Avoid letting surface water pool around your well.
    • Do not dispose of potentially hazardous materials down sinks or drains, especially if you have a septic system. 
    • Do not dispose of petroleum products, fertilizers, or pesticides by dumping them on the ground. 
    • Protect your well from vandalism, animal wastes, septic system discharge, and wildlife.